Incidence Of Proximal Junctional Kyphosis Research Articles

Health-related quality of life outcomes in adolescent Scheuermann's kyphosis patients treated with posterior spinal fusion: A comparison with age- and sex-matched controls.

Purpose:To assess the health-related quality of life and radiographic outcomes of surgically treated adolescent Scheuermann’s kyphosis patients after minimum of 2-year follow-up and to compare the health-related quality of life with age- and sex-matched healthy controls.Methods:Twenty-two consecutive adolescents (mean age = 16.7 years) undergoing posterior spinal fusion for Scheuermann’s kyphosis were included and matched by age and sex with two healthy controls. The health-related quality of life was evaluated using the Scoliosis Research Society-24 questionnaire. Radiographic parameters were measured for comparison preoperatively and at 6 months and 2-year follow-ups. The health-related quality of life parameters were compared with healthy controls at 2 years of follow-up.Results:The mean maximal thoracic kyphosis improved from 79° (range = 75°–90°) to 55° (range = 45°–75°) (p < 0.001), and the mean lumbar lordosis was reduced from 71° (range = 51°–107°) to 52° (range = 34°–68°) (p < 0.001) after 2 years postoperatively. Incidence of proximal junctional kyphosis (PJK) was 18%. The scores of the Scoliosis Research Society-24 improved, with statistical significance observed in pain and self-image domains from preoperative to 2-year follow-up (p = 0.002 in both domains). The self-image and function were significantly lower in the operated patients at their 2-year follow-up visit compared to controls (p = 0.023 for self-image and p < 0.001 for function).Conclusion:Instrumented posterior spinal fusion improves the health-related quality of life of Scheuermann’s kyphosis patients during the 2-year follow-up. The greatest improvement is observed in pain and self-image domains. The health-related quality of life in pain and activity domains reaches the level of healthy individuals, while function and self-image remain at a statistically lower level.

Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?

To investigate the relationship between pelvic incidence (PI) and proximal junctional kyphosis (PJK) in patients treated surgically for adult spinal deformity (ASD) with fusion from thoracolumbar junction to sacrum. A consecutive series of ASD patients who underwent fusion from the thoracolumbar junction to the sacrum with a minimum of 2-year follow-up was studied. Patients were divided into low PI (≤ 50°) and high PI (> 50°) groups. We compared radiographic parameters and the rates of PJK, between the two groups. A sub-analysis was performed on patients with a postoperative PI minus lumbar lordosis mismatch between - 10° and 10° (i.e., ideally corrected). Sixty-three patients were included: 19 low PI and 44 high PI. Median follow-up was 34months (range 24-103). Overall PJK rate was 38%. PJK was observed in 16% of low PI and 48% of high PI patients (p = 0.02). The odds ratio for developing PJK with a high PI compared to a low PI was 4.9 (p = 0.03). There were 32 ideally corrected patients. Eleven of these were in the low PI group, and 21 patients were in the high PI group. The incidence of PJK was 25% for ideally corrected patients. PJK occurred in none of these patients in the low PI group and 38% of patients in the high PI group (p = 0.03). When the upper-instrumented vertebra includes the thoracolumbar junction, patients with a PI > 50° are at a significantly higher risk of developing PJK compared to patients with a PI ≤ 50°.

Low-Density Pedicle Screw Constructs Are Associated with Lower Incidence of Proximal Junctional Failure in Adult Spinal Deformity Surgery.

Retrospective cohort study. Determine whether screws per level and rod material/diameter are associated with incidence of proximal junctional kyphosis (PJF). PJF is a common and particularly adverse complication of adult spinal deformity (ASD) surgery. There is evidence that the rigidity of posterior spinal constructs may impact risk of PJF. Patients with ASD and 2-year minimum follow-up were included. Only patients undergoing primary fusion of more than or equal to five levels with lower instrumented vertebrae (LIV) at the sacro-pelvis were included. Screws per level fused was analyzed with a cutoff of 1.8 (determined by receiver operating characteristic curve (ROC) analysis). Multivariable logistic regression was utilized, controlling for age, body mass index (BMI), 6-week postoperative change from baseline in lumbar lordosis, number of posterior levels fused, sex, Charlson comorbidity index, approach, osteotomy, upper instrumented vertebra (UIV), osteoporosis, preoperative TPA, and pedicle screw at the UIV (as opposed to hook, wire, etc.). In total, 504 patients were included. PJF occurred in 12.7%. The mean screws per level was 1.7, and 56.8% of patients had less than 1.8 screws per level. No differences were observed between low versus high screw density groups for T1-pelvic angle or magnitude of lordosis correction (both P > 0.15). PJF occurred in 17.0% versus 9.4% of patients with more than or equal to 1.8 versus less than 1.8 screws per level, respectively (P < 0.05). In multivariable analysis, patients with less than 1.8 screws per level exhibited lower odds of PJF (odds ratio (OR) 0.48, P < 0.05), and a continuous variable for screw density was significantly associated with PJF (OR 3.87 per 0.5 screws per level, P < 0.05). Rod material and diameter were not significantly associated with PJF (both P > 0.1). Among ASD patients undergoing long-segment primary fusion to the pelvis, the risk of PJF was lower among patients with less than 1.8 screws per level. This finding may be related to construct rigidity. Residual confounding by other patient and surgeon-specific characteristics may exist. Further biomechanical and clinical studies exploring this relationship are warranted.Level of Evidence: 3.

Correction to: Anterior versus posterior spinal fusion for Lenke type 5 adolescent idiopathic scoliosis: a systematic review and meta-analysis of comparative studies

PURPOSE To review and compare clinical and radiologic outcomes between anterior spinal fusion (ASF) and posterior spinal fusion (PSF) for the treatment of Lenke type 5 adolescent idiopathic scoliosis (AIS). METHODS A systematic review was performed according to Preferred reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. All level I-III evidence studies investigating the clinical and radiologic outcomes of ASF and PSF for the treatment of Lenke type 5 AIS were included. RESULTS Nine studies (285 ASF patients, 298 PSF patients) were included. ASF was associated with a significantly lower number of levels fused compared with PSF (p < 0.01) with similar immediate and long-term coronal deformity correction (p = 0.16; p = 0.12, respectively). PSF achieved a better correction of thoracic hypokyphosis in one study and lumbar hypolordosis in three studies. PSF was associated with a significant shorter length of stay (LOS) compared with ASF (p < 0.01). One long-term study demonstrated a significantly higher rate of proximal junctional kyphosis (PJK) with PSF compared with ASF. There were no significant differences in major complication or re-operation rates. CONCLUSION For the treatment of Lenke type 5 AIS, there is moderate evidence to suggest that ASF requires a lower number of instrumented levels to achieve similar immediate and long-term coronal deformity correction compared with PSF. There is some evidence to suggest that PSF may achieve better thoracic and lumbar sagittal deformity correction compared with ASF. There is some evidence to suggest a higher incidence of PJK at long-term follow-up with PSF compared with ASF. ASF is associated with a longer post-operative LOS compared with PSF.

Incidence and Radiological Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw Instrumentation with Rod Derotation and Direct Vertebral Rotation: A Minimum 5-Year Follow-Up Study.

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group (n = 62) and PJK group (n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively (p = 0.027), postoperatively (p = 0.001), and at last follow-up (p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

Effect of overcorrection on proximal junctional kyphosis in adult spinal deformity: analysis by age-adjusted ideal sagittal alignment

BACKGROUND CONTEXTThe effect of the degree of lumbar lordosis (LL) correction on proximal junctional kyphosis (PJK) has not been analyzed in context of the age-adjusted sagittal alignment goal. PURPOSETo determine the effect of sagittal correction on the incidence of PJK after an age-adjusted analysis in patients with adult spinal deformity (ASD). STUDY DESIGN/SETTINGRetrospective comparative study. PATIENT SAMPLESeventy-eight ASD patients who underwent deformity correction. OUTCOME MEASURESVisual analog scale (VAS), Oswestry Disability Index (ODI), and imaging. METHODSThis study included 78 ASD patients who underwent deformity correction and were followed-up more than 2 years. Patients were grouped according to the degree of LL correction relative to pelvic incidence (PI) by adjusting for age using the following formula: (age-adjusted ideal PI - LL) - (postoperative PI - LL). These were group U (undercorrection; <−10˚, N=15), group I (ideal correction; −10˚–10˚, N=34), and group O (over correction, >10˚, N=29). Various clinical and radiological parameters were compared among groups. The risk factors for PJK were also evaluated. RESULTSThe overall incidence of PJK was 32.1% (25/78), with significantly higher PJK rate in group O (48.3%) compared with groups U (13.3%) and I (26.5%) (p=.041). The degree of postoperative LL correction relative to the PI by adjusting for age was a risk factor for the development of PJK (11.4° for PJK vs. 0.2° for non-PJK, p=.033). In addition, 2-year postoperative VAS (7.0 vs. 3.4, p<.001) and ODI (28.9 vs. 24.8, p=.040) scores were significantly higher in the PJK group than in the non-PJK group. A small PI (PI < 45°) was associated with a tendency of overcorrection (73.3%, P < 0.001) and thereby with the high incidence of PJK (53.3%, p=.005). CONCLUSIONSOvercorrection of LL relative to PI considering age-adjusted ideal sagittal alignment tends to increase the incidence of PJK. The incidence of PJK is expected to be high in patients with low PI (<45°) because of the tendency of overcorrection. To reduce the risk of PJK, surgeons should take age-adjusted parameters into account and exercise caution not to overcorrect patients with low PI, since this can result in suboptimal clinical outcomes.

Anterior versus posterior spinal fusion for Lenke type 5 adolescent idiopathic scoliosis: a systematic review and meta-analysis of comparative studies.

To review and compare clinical and radiologic outcomes between anterior spinal fusion (ASF) and posterior spinal fusion (PSF) for the treatment of Lenke type 5 adolescent idiopathic scoliosis (AIS). A systematic review was performed according to Preferred reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. All level I-III evidence studies investigating the clinical and radiologic outcomes of ASF and PSF for the treatment of Lenke type 5 AIS were included. Nine studies (285 ASF patients, 298 PSF patients) were included. ASF was associated with a significantly lower number of levels fused compared with PSF (p < 0.01) with similar immediate and long-term coronal deformity correction (p = 0.16; p = 0.12, respectively). PSF achieved a better correction of thoracic hypokyphosis in one study and lumbar hypolordosis in three studies. PSF was associated with a significant shorter length of stay (LOS) compared with ASF (p < 0.01). One long-term study demonstrated a significantly higher rate of proximal junctional kyphosis (PJK) with PSF compared with ASF. There were no significant differences in major complication or re-operation rates. For the treatment of Lenke type 5 AIS, there is moderate evidence to suggest that ASF requires a lower number of instrumented levels to achieve similar immediate and long-term coronal deformity correction compared with PSF. There is some evidence to suggest that PSF may achieve better thoracic and lumbar sagittal deformity correction compared with ASF. There is some evidence to suggest a higher incidence of PJK at long-term follow-up with PSF compared with ASF. ASF is associated with a longer post-operative LOS compared with PSF.

Surgical Procedures Used for Correction of Scheuermann's Kyphosis: A Meta-Analysis.

Objectives Scheuermann's kyphosis can cause severe back pain and cosmetic disorders to patients. Previous studies on surgical procedure selection for correction of Scheuermann's kyphosis have drawn controversial conclusions. Here, a meta-analysis was performed to figure out a better way between anterior-posterior (AP) combined procedures and posterior-only (PO) procedures. Methods We searched PubMed database and Ovid database, as well as Cochrane Library (between January 2009 and December 2020, around recent ten years), for studies reporting Scheuermann's kyphosis correction in an anterior way or a posterior way. Random effects meta-analysis regarding correction degrees and incidence of proximal junctional kyphosis (PJK) was performed. Results Finally, 13 unique studies including 586 patients (AP: 300; PO: 286) were identified and included for this meta-analysis. Overall, 6 AP cohorts and 10 PO cohorts were pooled regarding the correction degrees of kyphosis in the analysis, respectively. Pooled correction degrees in AP cohorts were 33.31 (95% CI: 27.48–39.15; I2 = 86%, P < 0.001) and in PO cohorts were 31.16 (95% CI: 26.97–35.35; I2 = 81.1%, P < 0.001). Comparison of correction between AP and PO cohorts did not indicate any significant difference. Likewise, postoperative PJK incidence showed no difference. Back pain can be caused by both AP and PO procedures, but which causes less pain remains to be conclusive. The PO approach showed less blood loss and shorter surgical duration as compared to the AP approach. Conclusions In summary, this meta-analysis shows similar treatment effects between AP and PO procedures in correcting Scheuermann's kyphosis, suggesting the advantage of PO procedures due to less blood loss and surgical duration. However, the postoperative complications PJK and distal junctional kyphosis (DJK) cannot be well concluded due to the limitation of existing data.

Determination of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Correction Fusion using Pedicle Screw Versus Hook Plus Screw Pedicle Instrumentation

Introduction: Spinal instrumentation in idiopathic adolescent scoliosis (AIS) aims to correct spinal deformity, and maintain spinal stability. Proximal junctional kyphosis (PJK) is a relatively common postoperative complication. Posterior-only fusion using diverse instruments such as pedicle screw and hybrid hook plus screw is favored to correct spinal deformity. The current study aims to compare PJK incidence between pedicle screw versus hybrid hook plus screw.&#x0D; Methods: This non-randomized clinical trial has been conducted on 71 AIS patients undergone posterior-only spinal deformity fusion using pedicle screw only (n=42) or hook plus pedicle (n=29) implantation in 2015-20. The proximal thoracic (PT), main thoracic (MT), T5-T12 sagittal Cobb angles and proximal junctional angle (PJA) were evaluated through radiographies taken at baseline, immediately postoperative, within 6 and 18 months. PJK was defined as PJA &gt;10 degrees. &#x0D; Results: Using both pedicle screw only and hook plus pedicle have led to significant improvement in MT, PT, PJA and T5-T12 angles (P-value&lt;0.05); however, the two groups were not statistically different (P-value&gt;0.05). Seventeen cases (23.9%) presented PJK among which 11 (26.2%) and 6 (20.7%) ones were in the predicle screw versus hook plus screw implantation groups, respectively (P-value=0.54). The comparison of PJA and T5-T12 Cobb angles revealed significant difference between the PJK versus non-PJK cases (P-value&lt;0.05).&#x0D; Conclusion: AIS instrumentation was accompanied by satisfying outcomes using pedicle screw or hook plus screw. However, none of the applied instruments was superior over the other; PJK occurred in fewer cases undergone posterior-only approach of AIS correctional surgery using hook and screw.

P90. To prevent PJK in Scheuermann's Kyphosis, restore kyphosis to patient's PI value and choose proximal UIV

<h3>BACKGROUND CONTEXT</h3> Incidence of proximal junctional kyphosis (PJK) in Scheuermann's Kyphosis (SK) varies between 24–40%. Multiple factors have been implicated, including: overcorrection of kyphosis, failure to include the proximal end vertebra and choice of implants. Recently, studies have attempted to analyze pelvic parameters in SK, including lumbopelvic mismatch. However, the issue remains unresolved. <h3>PURPOSE</h3> This study aimed to determine the goal correction parameters based upon patients' kyphosis, pelvic incidence, and UIV to prevent PJK in Scheuermann's Kyphosis. <h3>STUDY DESIGN/SETTING</h3> Retrospective Chart Review. <h3>PATIENT SAMPLE</h3> A total of 96 Sheuermann Kyphosis patients undergoing correction procedures with all pedicle screws (PS), hybrid fixation (HF) or anterior/posterior fusions with hybrid fixation (AP). <h3>OUTCOME MEASURES</h3> Kyphosis minus pelvic incidence > -10° was determined to be normal. T1/T2 were grouped together as proximal fusion group compared to T3 and distal group. <h3>METHODS</h3> X-ray and chart review of all SK patients analyzed and compared. <h3>RESULTS</h3> 96 total patients: PS (n=41), HF (n=24), and AP (n=31). Overall, at early postop 12/96 (12.5%) patients had PJK. At final follow-up 33/96 (34.4%) had PJK. There was no significant difference between groups at early postop (p = 0.86) or final follow-up (p = 0.67). When correcting Kyphosis-PI to > -10° and UIV was chosen to be T1 or T2, PJK developed in 6% of patients. When fusing to T1/T2 and having kyphosis-PI < -10°, 38.9% of patients developed PJK.When having Kyphosis-PI to > -10° but UIV chosen at T3 or below, 77.8% of patients developed PJK. When fusing to T3 or below and failing to correct kyphosis-PI to > -10°, 37% of patients developed PJK. <h3>CONCLUSIONS</h3> While surgical techniques and implants do not seem to have a substantial role in development of PJK, selecting proximal UIV and avoiding Kyphosis-PI mismatch can significantly decrease this possibility. Surgeons treating Scheuermann's Kyphosis should, therefore, aim to correct kyphosis closer to patient's pelvic incidence. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Instrumentation Techniques to Prevent Proximal Junctional Kyphosis and Proximal Junctional Failure in Adult Spinal Deformity Correction: A Systematic Review of Clinical Studies.

Study Design:Systematic review.Objectives:To summarize the results of clinical studies investigating spinal instrumentation techniques aiming to reduce the postoperative incidence of proximal junctional kyphosis (PJK) and/or failure (PJF) in adult spinal deformity (ASD) patients.Methods:EMBASE and Medline® were searched for articles dating from January 2000 onward. Data was extracted by 2 independent authors and methodological quality was assessed using ROBINS-I.Results:18 retrospective- and prospective cohort studies with a severe or critical risk of bias were included. Different techniques were applied at the upper instrumented vertebra (UIV): tethers in various configurations, 2-level prophylactic vertebroplasty (2-PVP), transverse process hooks (TPH), flexible rods (FR), sublaminar tapes (ST) and multilevel stabilization screws (MLSS). Compared to a pedicle screw (PS) group, significant differences in PJK incidence were found using tethers in various configurations (18% versus 45%, P = 0.001, 15% versus 38%, P = 0.045), 2-PVP (24% vs 36%, P = 0.020), TPH (0% vs. 30%, P = 0.023) and FR (15% versus 38%, P = 0.045). Differences in revision rates for PJK were found in studies concerning tethers (4% versus 18%, P = 0.002), 2-PVP (0% vs 13%, P = 0.031) and TPH (0% vs 7%, P = n.a.).Conclusion:Although the studies are of low quality, the most frequently studied techniques, namely 2-PVP as anterior reinforcement and (tensioned) tethers or TPH as posterior semi-rigid fixation, show promising results. To provide a reliable comparison, more controlled studies need to be performed, including the use of clinical outcome measures and a uniform definition of PJF.

Proximal junctional kyphosis is a rebalancing spinal phenomenon due to insufficient postoperative thoracic kyphosis after adolescent idiopathic scoliosis surgery.

Many authors tried to explain proximal junctional kyphosis (PJK) after adolescent idiopathic scoliosis (AIS) surgery by looking for risk factors. Latest publications focus on sagittal alignment. Each healthy adolescent has a specific thoracic kyphosis (TK) depending on their pelvic parameters and lumbar lordosis (LL). The objective of this work is to determine if the difference between TK at follow-up (TKFU) and the patient-specific TK (PSTK) plays a role in PJK occurrence after AIS surgery. The secondary objective was to find other risk factors. We analyzed retrospectively 570 thoracic AIS who underwent a posterior thoracic fusion from nine centers. The series was separated in two groups: with and without PJK. PSTK was calculated with the formula PSTK = 2(PT + LL-PI). TK Gap was the difference between TKFU and PSTK. Logistic regression was utilized to test the impact of TK Gap and other known risk factors on PJK occurrence. Univariate analysis showed 15 factors significantly different between the groups. In a multivariate analysis, three factors had a strong significant influence on PJK: TKFU, TK Gain and TK Gap. Four additional factors affected the rate of PJK: Posterior translation on two rods, preoperative TK, preoperative LL and number of instrumented vertebrae. PJK is related to the insufficient TK at follow-up, compared to the specific TK that every patient should have according to their pelvic parameters. PJK incidence is significantly reduced by a strong gain in TK and a thoracic selective fusion which leaves the proximal lumbar vertebrae free. Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Proximal Fixation in Adolescent Scoliosis Lenke 1 and 3 Treated by Posteromedial Translation Using Sublaminar Bands: Transverse-pedicular Hook Claw Versus Transverse Hook-pedicular Screw Claw.

This is retrospective comparative study. Numerous studies have focused on the efficacy, safety, and restoration of thoracic kyphosis in adolescent idiopathic scoliosis surgery using posteromedial translation method with sublaminar bands and hook claws at the top. The relevance of exchanging the penultimate anchor, that is, the pedicle hook with a pedicle screw in a hybrid construction has not yet been assessed. Our objective was to assess, in adolescent scoliosis Lenke 1 and 3 operated by posteromedial translation using sublaminar bands, the proximal fixation claw influence (transverse-pedicular hook vs. transverse hook-pedicular screw) for postoperative correction and the proximal junctional kyphosis (PJK) at 2 years follow-up. A comparative monocentric retrospective study included adolescent idiopathic scoliosis thoracic requiring surgery, between 2015 and 2017, with 2 years follow-up. Clinical (complications, revision surgery, and scoliosis research society-30) and radiographic (coronal and sagittal parameters) assessment were reported. Radiologic PJK was defined by a proximal junctional angle increase of 10 degrees or more between postoperative period and the last follow-up. Sixty patients (age at surgery=16±2 y; mean Cobb angle=58.2±12 degrees) were divided into 2 similar groups according to upper fixation: transverse-pedicular hook (H-H) and transverse hook-pedicle screw (S-H). No statistical differences were found for correction parameters (P>0.05). We reported 2 cases of PJK in H-H group (N=2/30=6.6%) and none in S-H group (N=0/30) (P=0.1) none requiring revision. No infectious or neurological events were reported. Mean scoliosis research society-30 was 126±12.7 in H-H group whereas 129.3±10 in S-H group (P=0.4). No differences in postoperative correction and clinical results at 2 years follow-up were found. A claw with transverse-pedicular hook increase proximal junctional angle without significant increase on radiographic PJK incidence compared with a claw with transverse hook and pedicle screws.

Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

BACKGROUND CONTEXTAdult spinal deformity patients treated operatively by long-segment instrumented spinal fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the proximal end of spinal instrumentation may reduce the incidence of PJK and PJF, however, previously evaluated techniques have not directly been compared. PURPOSETo determine the biomechanical characteristics of five different posterior spinal instrumentation techniques to achieve semirigid junctional fixation, or “topping-off,” between the rigid pedicle screw fixation (PSF) and the proximal uninstrumented spine. STUDY DESIGNBiomechanical cadaveric study. METHODSSeven fresh-frozen human cadaveric spine segments (T8–L3) were subjected to ex vivo pure moment loading in flexion-extension, lateral bending and axial rotation up to 5 Nm. The native condition, three-level PSF (T11–L2), PSF with supplemental transverse process hooks at T10 (TPH), and two sublaminar taping techniques (knotted and clamped) as one- (T10) or two-level (T9, T10) semirigid junctional fixation techniques were compared. The ROM and neutral zone (NZ) of the segments were normalized to the native condition. The linearity of the transition zones over three or four segments was determined through linear regression analysis. RESULTSAll techniques achieved a significantly reduced ROM at T10-T11 in flexion-extension and axial rotation relative to the PSF condition. Additionally, both two-level sublaminar taping techniques (CT2, KT2) had a significantly reduced ROM at T9-T10. One-level clamped sublaminar tape (CT1) had a significantly lower ROM and NZ compared with one-level knotted sublaminar tape (KT1) at T10-T11. Linear regression analysis showed the highest linear correlation between ROM and vertebral level for TPH and the lowest linear correlation for CT2. CONCLUSIONSAll studied semirigid junctional fixation techniques significantly reduced the ROM at the junctional levels and thus provide a more gradual transition than pedicle screws. TPH achieves the most linear transition over three vertebrae, whereas KT2 achieves that over four vertebrae. In contrast, CT2 effectively is a one-level semirigid junctional fixation technique with a shift in the upper rigid fixation level. Clamped sublaminar tape reduces the NZ greatly, whereas knotted sublaminar tape and TPH maintain a more physiologic NZ. Clinical validation is ultimately required to translate the biomechanics of various semirigid junctional fixation techniques into the clinical goal of reducing the incidence of proximal junctional kyphosis and failure. CLINICAL SIGNIFICANCEThe direct biomechanical comparison of multiple instrumentation techniques that aim to reduce the incidence of PJK after thoracolumbar spinal fusion surgery provides a basis upon which clinical studies could be designed. Furthermore, the data provided in this study can be used to further analyze the biomechanical effects of the studied techniques using finite element models to better predict their post-operative effectiveness.

State of the art: proximal junctional kyphosis-diagnosis, management and prevention.

Proximal junctional kyphosis (PJK) is a common problem that may occur following the surgical treatment of adult patients with spinal deformity. It is defined as the proximal junctional sagittal angle from the UIV and UVI + 2 of at least 10° AND at least 10° greater than the preop measurement. The reported incidence of radiographic PJK in the literature varies between 17 and 46%. A smaller subset of these patients may need revision surgery and are defined as proximal junctional failure (PJF), which can be associated with vertebral fracture, vertebral subluxation, failure of instrumentation, and neurological deficits. Several risk factors for development of PJK have been proposed. However, large-scale prospective studies are needed to better identify strategies to reduce the incidence of PJK.

Degenerative lumbar scoliosis patients with proximal junctional kyphosis have lower muscularity, fatty degeneration at the lumbar area.

To assess the lumbar muscle conditions on the incidence of proximal junctional kyphosis (PJK) after long-level correction and instrumentation surgery for degenerative lumbar scoliosis (DLS) patients with a minimum 2-year follow-up. Eighty-four DLS patients undergoing long instrumented fusion surgery (≥ 5 vertebrae) were retrospectively studied. According to the occurrence of PJK at the final follow-up, patients were divided into the PJK group and the Non-PJK group. Patient characteristics, surgical variables and radiographic parameters were analyzed statistically. The lumbar muscularity (cross-sectional area of muscle-disc ratio × 100) and fatty degeneration (signal intensity of muscle-subcutaneous fat ratio × 100) were evaluated on magnetic resonance imaging . The prevalence of PJK was 20.24%. Gender, age at surgery, body mass index, uppermost instrumented vertebrae level, fusions extending to the sacrum, and levels fused were not significantly different between the groups. Lower bone mineral density, smaller functional cross-sectional area (FCSA) of paraspinal extensor muscles (PSE), higher lean muscle-fat index and total muscle-fat index of PSE, greater preoperative thoracolumbar kyphosis (TLK), smaller preoperative sacral slope (SS), larger preoperative sagittal vertical axis were identified in PJK group. Logistic regression analysis showed that osteoporosis, preoperative TLK > 15°, SS > 24°, FCSA of PSE > 138.75, and total muscle-fat index of PSE > 4.08 were independently associated with PJK. The final follow-up VAS score for back pain was higher, and SRS-22 subcategories of pain, function, self-image, and total score were significantly lower in the PJK group. Osteoporosis, lower lumbar muscularity and higher fatty degeneration, preoperative greater TLK and smaller SS were found to be strongly associated with the presence of PJK in DLS.

Preoperative Hounsfield Units at the Planned Upper Instrumented Vertebrae May Predict Proximal Junctional Kyphosis in Adult Spinal Deformity.

Retrospective cohort study. To investigate the association between Hounsfield units (HU) measured at the planned upper instrumented vertebra (UIV) and UIV+1 and proximal junctional kyphosis (PJK) in patients with adult spinal deformity (ASD). PJK is a common complication following surgery for ASD and poor bone quality is noted to be one of the risk factors. HUs from standard computed tomography (CT) scans can be used for evaluating regional bone quality. Sixty-three patients were included from a single institution. The demographic characteristics and radiographic parameters were recorded. Local vertebral HUs at the planned UIV and UIV+ 1 were measured using preoperative CT scans. The patients were divided into three groups: no PJK, non-bony PJK, and bony PJK. The risk factors between the three groups and the correlation between the mean HU and increase in the PJK angle were analyzed. The incidence of PJK was 36.5%. The mean HU was significantly lower in the bony PJK group (HU: 109.0) than in the no PJK group (HU: 168.7, P = 0.038), and the mean HU in the non-bony PJK group (HU: 141.7) was not different compared to the other two groups. There was a significant negative correlation between the mean HU values and the increase in the PJK angles (r = -0.475, P < 0.01). The cutoff value for the mean HU used to predict bony PJK was 120 and a HU value less than 120 was a significant risk factor for bony PJK (OR: 5.74, 95% CI [1.01-32.54], P = 0.04). We noted a significant inverse relationship between the mean HUs at the UIV and UIV+ 1 and increase in the PJK angles postoperatively. In ASD patients, the HUs may be used preoperatively to identify patients with a higher risk of bony PJK.Level of Evidence: 3.

Semitendinosus Tendon Augmentation for Prevention of Proximal Junctional Failure.

Retrospective cohort study. The aim of this study was to compare the incidence of proximal junctional kyphosis (PJK), proximal junctional failure (PJF), and clinical outcomes of patients who did and did not receive posterior ligament complex (PLC) augmentation using a semitendinosus allograft when undergoing long-segment posterior spinal fusion for adult spinal deformity. Clinical research on the augmentation of the PLC to prevent PJK and PJF has been limited to small case series without a comparable control group. From 2014 to 2019, a consecutive series of patients with adult spinal deformity who underwent posterior long-segment spinal fusion with semitendinosus allograft to augment the PLC (allograft) or without PLC augmentation (control) were identified. Preoperative and postoperative spinopelvic parameters were measured. PJK, PJF, and Oswestry Disability Index (ODI) scores were recorded and compared between the two groups. Univariate and multivariate analysis was performed. P ≤ 0.05 was considered significant. Forty-nine patients in the allograft group and 34 patients in the control group were identified. There were no significant differences in demographic variables or operative characteristics between the allograft and control group. Preoperative and postoperative spinopelvic parameters were also similar between the two groups. PJK was present in 33% of patients in the allograft group and 32% of patients in the control group (P = 0.31). PJF did not occur in the allograft group, whereas six patients (18%) in the control group developed PJF (P = 0.01). Postoperative absolute ODI was significantly better in the allograft group (P = 0.007). The utilization of semitendinosus allograft tendon to augment the PLC at the upper instrumented vertebrae in patients undergoing long-segment posterior spinal fusion for adult deformity resulted in a significant decrease in PJF incidence and improved functional outcomes when compared to a cohort with similar risk of developing PJK and PJFLevel of Evidence: 3.

Comparison of Proximal Junctional Failure and Functional Outcomes Across Varying Definitions of Proximal Junctional Kyphosis

Proximal junctional kyphosis (PJK) is a well-recognized complication following surgery for adult spinal deformity (ASD); however, definitions for PJK and its clinical implications can significantly vary by study. This study compares multiple definitions of PJK and describes incidence and clinical significance by definition. From 2014 to 2019, patients with ASD who underwent spinal fusion were identified. Nine definitions of PJK were created based on previously established definitions using the following upper instrumented vertebra+2 (UIV+2) sagittal Cobb measurements: A= ≥10 postoperative AND preoperative, B= ≥10 postoperative, C=≥10 preoperative, D= ≥15 postoperative AND preoperative, E= ≥15 postoperative, F= ≥15 preoperative, G= ≥20 postoperative AND preoperative, H= ≥20 postoperative, I= >20 preoperative. Incidence of PJK was calculated by definition. Area under the curve (AUC) was calculated based on a receiver operating characteristic to assess ability to predict proximal junctional failure (PJF). Univariate analysis was performed to assess association with postoperative Oswestry Disability Index (ODI) scores. Across 82 patients, the incidence of PJK and AUC by definition was as follows: A= 47%, 0.47; B= 72%, 0.65; C= 49%, 0.45; D= 27%, 0.46; E= 57%, 0.62; F=27%, 0.46; G= 10%, 0.55; H= 40%, 0.71; I= 10%, 0.55. No definition was associated with postoperative ODI scores (P < 0.05). The incidence of PJK significantly decreased with stricter definitions. Definitions utilizing only postoperative UIV+2 values had higher incidences but were more likely to capture patients who developed PJF. No definition was associated with postoperative ODI scores. UIV+2 ≥20 was best in distinguishing patients who developed PJF.

Proximal Junctional Kyphosis and Proximal Junctional Failure in the Treatment for Adult Spinal Deformity: Definitions and Epidemiology

Proximal junctional failure (PJF) is considered to be one of the most serious complications after correction surgery with a long construct for adult spinal deformity. Proximal junctional kyphosis (PJK) was first defined as an angle between the lower endplate of the uppermost instrumented vertebra (UIV) and the upper endplate of UIV+2 of 10 degrees or greater, and at least 10 degrees greater than the preoperative measurement. Although PJK has been found to cause no significant clinical symptoms, PJF is regarded as a pathology associated with a fracture of UIV or UIV+1, posterior osseoligamentous disruption, or a pullout of instrumentation at the UIV, and may require revision surgery. The incidence of PJK or PJF is influenced by a variety of factors including the pathology of the deformity, surgical procedures and spinal construct, status of osteoporosis, prophylactic procedures, and the follow-up period. Therefore, the reported incidences of PJK vary widely, from 7.7% to 56%, whereas those of PJF vary widely, from 1.4% to 35%.