Supplemental Fixation Research Articles

Reamed intramedullary nailing of diaphyseal multifragmentary femur fractures (AO/OTA 32-C) without fluoroscopy guidance: prospective analysis of methods and short-term outcomes in a low-resource setting.

To describe the methods and outcomes of reamed intramedullary nailing (IMN) of diaphyseal multifragmentary femur (AO/OTA C2 and C3) fractures (DMFFs) in a low-resource setting without fluoroscopy and fracture table. The prospective study involved 35 DMFFs among 318 femur fractures treated ≤ 3weeks post-injury with SIGN nails. The fractures were fixed without fluoroscopy, fracture table and power reaming. Closed, mini-open or open reduction was done. Anatomical length and alignment were ensured using a surgical support triangle during retrograde nailing, and by an assistant during antegrade nailing. Follow-ups were done at 6weeks, 12weeks and 6months. DMFFs constituted 11.0% of the 318 fractures. Twenty-four (68.6%) were males. The mean age was 39.0years (range 17-75years). About 94.3% were injured in road traffic accidents. Fracture reduction was closed in 18, mini-open in 8 and full-open in 9. The operative times were significantly shorter for closed than open reduction (p = 0.001). Five fractures received a supplemental fixation with plate or lag screws. By the 12th post-operative week, 97.1% demonstrated continuing radiographic healing, 94.1% tolerated painless weight-bearing and 91.2% could squat & smile. There was no infection or noticeable rotational malunion. Five fractures healed with a limb-length discrepancy of < 2cm. The study demonstrates the feasibility of reamed IMN of DMFFs without fluoroscopy. The outcomes were satisfactory. Although the small sample size and short follow-up period are limitations, the study could serve as a basis for future larger studies in low-resource settings.

Finite element analysis of proximal femur bionic nail for treating intertrochanteric fractures in osteoporotic bone

This study compared the biomechanical characteristics of proximal femur bionic nail (PFBN) and proximal femoral nail antirotation (PFNA) in treating osteoporotic femoral intertrochanteric fractures using finite element analysis. Under similar bone density, the PFBN outperforms the PFNA in maximum femoral displacement, internal fixation displacement, stress distribution in the femoral head and internal fixation components, and femoral neck varus angle. As the bone density decreases, the PFBN’s biomechanical advantages over PFNA become more pronounced. This finding suggests that the PFBN is superior for treating osteoporotic intertrochanteric femoral fractures.

Is 3D-printed self-stabilizing endoprosthesis reconstruction without supplemental fixation following total sacrectomy a viable approach for sacral tumours?

The spinopelvic reconstruction poses significant challenges following total sacrectomy in patients with malignant or aggressive benign bone tumours encompassing the entire sacrum. In this study, we aim to assess the functional outcomes and complications of an integrated 3D-printed sacral endoprostheses featuring a self-stabilizing design, eliminating the requirement for supplemental fixation. We retrospectively analyzed patients with sacral tumours who underwent total sacrectomy followed by reconstruction with 3D-printed self-stabilizing endoprosthesis. Clinically, we evaluated functional outcomes using the 1993 version of the musculoskeletal tumour society (MSTS-93) score. Perioperative and postoperative complications were also documented. 10 patients met final inclusion criteria. The median age was 49years (range, 31-64years). The median follow-up time was 26.5months (range, 15-47months). Median postoperative functional MSTS-93 was 22.5 (range, 13-25). The median operation time was 399.5min (305-576min), and the median intraoperative blood loss was and 3200ml (2400-7800ml). Complications include wound dehiscence in one patient, bowel, bladder, and sexual dysfunction in four patients, cerebrospinal fluid leak in one patient, and tumour recurrence in one patient. There were no mechanical complications related to the endoprosthesis at the last follow-up. The utilization of 3D-printed self-stabilizing endoprosthesis proved to be a viable approach, yielding satisfactory short-term outcomes in patients undergoing total sacral reconstruction without supplemental fixation.

What to Expect? Use of Supplemental Fixation With a Concomitant Dorsal Spanning Plate for Complex Intraarticular Distal Radius Fractures.

The dorsal spanning plate (DSP) is a versatile implant suitable for bridging severely comminuted intraarticular distal radius fractures [AO (Arbeitsgemeinschaft für Osteosynthesefragen) 23-C.1-C.3]. It may be used alone or with supplemental fixation such as a volar locking plate (VLP) or fragment-specific fixation (FSF). Outcomes following DSP fixation with additional implants have not been specifically evaluated. We retrospectively reviewed consecutive patients who underwent internal fixation of a distal radius fracture by a single surgeon from 2017 to 2021. Patients were grouped according to implants used: DSP only, DSP + FSF, and DSP + VLP. Preoperative variables, treatment times, and wrist range of motion (ROM) were assessed. Functional wrist ROM was defined as minimum 80° combined flexion and extension. One hundred fifty-two patients underwent surgery for wrist fracture, 33 of them were treated with a DSP: 8 DSP only, 6 DSP + VLP, and 19 DSP + FSF. Falls from height greater than 10 ft accounted for 52% of injuries, most of which were treated with a DSP + FSF. Treatment times and ROM were similar between subgroups. Wrist ROM did not improve significantly beyond 4 weeks following DSP removal. Overall, DSP patients recovered a mean wrist ROM of 85° (range 0°-130°) within a median 26 weeks total treatment period (range 12-68 weeks). Regardless of the construct used, if the distal radius articular surface is well reduced and other principles of fracture fixation are applied, most patients treated with a DSP can expect to regain functional wrist ROM. Level IV-Retrospective review of prospectively collected data.

Osteochondral autograft and allograft for knee cartilage injuries—an international Delphi consensus statement

IntroductionArticular cartilage injuries of the knee are a complex and challenging clinical pathology. ObjectivesThe purpose of this study was to establish consensus statements via a Delphi process on osteochondral autograft (OATS) and osteochondral allograft (OCA) in the setting of cartilage defects in the knee. MethodsA consensus process on knee cartilage injuries utilizing a modified Delphi technique was conducted. Seventy-nine surgeons across 17 countries participated in these consensus statements. Twenty-seven questions were generated on OATS and OCA, with 3 rounds of questionnaires and final voting occurring. Consensus was defined as achieving 80% to 89% agreement, whereas strong consensus was defined as 90% to 99% agreement, and unanimous consensus was defined as 100% agreement with a proposed statement. ResultsOf the 27 total questions and consensus statements on OATS and OCA developed from 3 rounds of voting, 0 achieved unanimous consensus, 11 achieved strong consensus, 7 achieved consensus, and 9 did not achieve consensus. ConclusionsThe statements that achieved strong consensus pertained to the contraindications of OATS and OCA, the preferred site for harvest, storage conditions and timeframe for grafting, site preparation, surgical approach, graft step-off, impact of multiple grafts on clinical outcome, and ways to minimize complications. The statements that did not reach consensus regarded indications for OATS, locations for OATS and OCA, backfilling, sizing, supplemental fixation, marrow venting, and the use of orthobiologics for OCA.

Biphasic Calcium Phosphate Bone Graft With a Unique Surface Topography: A Single-Center Ambispective Study for Degenerative Disease of the Lumbar Spine.

This study is an ambispective evaluation and analysis of a single-center cohort. This study aimed to evaluate the performance of a novel biphasic calcium phosphate (BCP) bone graft with submicron-sized needle-shaped surface topography (BCP<µm) in interbody arthrodesis of the lumbar spine. This study was a single-center ambispective assessment of adult patients receiving BCP<µm as part of their lumbar interbody fusion surgery. The primary outcome was a fusion status on computed tomography (CT) 12months postoperative. The secondary outcomes included postoperative changes in the visual analogscale (VAS), Oswestry Disability Index (ODI), Short Form 12 (SF-12), and length of stay (LOS). Sixty-three patients with one- to three-level anterior (48, 76%) and lateral (15, 24%) interbody fusions with posterior instrumentation were analyzed. Thirty-one participants (49%) had three or more comorbidities, including heart disease (43 participants, 68%), obesity (31 participants, 49%), and previous lumbar surgery (23 participants, 37%). The mean ODI decreased by 24. The mean SF-12 physical health and SF-12 mental health improved by a mean of 11.5 and 6.3, respectively. The mean VAS for the left leg, right leg, and back improved by a mean of 25.75, 22.07, and 37.87, respectively. Of 101 levels, 91 (90%) demonstrated complete bridging trabecular bone fusion with no evidence of supplemental fixation failure. The data of BCP<µm in interbody fusions for degenerative disease of the lumbar spine provides evidence of fusion in a complicated cohort of patients.

How modular porous metal augments have changed the management of acetabular bone loss at primary or revision total hip arthroplasty.

The advent of modular porous metal augments has ushered in a new form of treatment for acetabular bone loss. The function of an augment can be seen as reducing the size of a defect or reconstituting the anterosuperior/posteroinferior columns and/or allowing supplementary fixation. Depending on the function of the augment, the surgeon can decide on the sequence of introduction of the hemispherical shell, before or after the augment. Augments should always, however, be used with cement to form a unit with the acetabular component. Given their versatility, augments also allow the use of a hemispherical shell in a position that restores the centre of rotation and biomechanics of the hip. Progressive shedding or the appearance of metal debris is a particular finding with augments and, with other radiological signs of failure, should be recognized on serial radiographs. Mid- to long-term outcomes in studies reporting the use of augments with hemispherical shells in revision total hip arthroplasty have shown rates of survival of > 90%. However, a higher risk of failure has been reported when augments have been used for patients with chronic pelvic discontinuity.

Cementless Total Hip Arthroplasty With Paavilainen Femoral Shortening Osteotomy Can Provide Good Results at 10 Years in Patients Who Have Crowe IV Developmental Dysplasia of the Hip

BackgroundThe aim of this study was to present the clinical and radiologic results of primary total hip arthroplasty (THA) using the femoral shortening osteotomy technique described by Paavilainen in patients who have Crowe IV developmental dysplasia of the hip. MethodsWe retrospectively analyzed the results of primary THA using the Paavilainen technique in 335 hips. The mean follow-up was 10.2 years. The degree of limp, leg-length discrepancy, and patient satisfaction were assessed. The Oxford Hip Score was used to examine functional outcomes. A number of radiographic parameters were also assessed. ResultsThe most common reason for revision surgery was nonunion of the distally advanced greater trochanter. This complication was observed in 22 hips (6.5%). The 10-year survival for acetabular components, it was 97.3%, and for femoral components was 98.7% with aseptic loosening as the end point, and 85.9% with reoperation for any reason as the end point. Patients demonstrated improved functional outcomes. The mean limb lengthening was 27.8 mm. Nonunion was more common if the contact length of the proximal femoral fragment with the lateral surface of the distal femoral fragment was less than 35 mm. ConclusionsCementless primary THA using the femoral shortening osteotomy technique described by Paavilainen in patients who have Crowe IV dysplasia of the hip demonstrates good clinical and radiologic postoperative results. If the contact between the fragments after osteotomy is less than 35 mm, there is a high risk of nonunion, and supplemental fixation may be warranted.

Acute Patellar Tendon Ruptures: An Update on Management.

Patellar tendon ruptures can be debilitating injuries. When incomplete, partial tears can be managed nonsurgically with immobilization and progressive rehabilitation. Although complete ruptures remain a relatively uncommon injury, they portend a high level of morbidity. Ruptures typically result from an acute mechanical overload to the extensor mechanism, such as with forced quadriceps contraction and knee flexion. However, chronically degenerated tendons are also predisposed to failure from low-energy injuries. Diagnosis can often be made clinically with recognition of a palpable defect to the tendon, localized patellar tendon tenderness, and inability to actively extend the knee. Diagnosis and surgical planning can be established with radiograph, ultrasonography, or magnetic resonance imaging. Surgical repair is the mainstay of treatment, and there have been many recent advances in repair technique, optimal reconstruction strategies, and supplemental fixation. Time to surgery for complete tears remains the most important prognosticator for success. Direct primary repair can be completed with transosseous tunnels, suture anchor repair, or end-to-end repair. Tendon reconstruction can be achieved with or without mechanical or biologic augments. Rehabilitation programs vary in specifics, but return to sport can be expected by 6 months postoperatively.

466 Primary Anterior Lumbar Interbody Fusion, With and Without Posterior Instrumentation: A 1377 Patient Cohort From a Multicenter Spine Registry

INTRODUCTION: Anterior lumbar interbody fusion (ALIF) is a versatile and powerful technique for a variety of lumbar degenerative pathologies. Adding posterior supplementary fixation to ALIF (ALIF+PSF) is common and may confer benefits in terms of higher fusion rate but could contribute to adjacent segment disease (ASD) due to additional rigidity. METHODS: Adult patients who underwent primary ALIF for lumbar degenerative pathology between levels L4-S1 over a 12-year period were included. Cases of trauma, cancer, infection, supplemental decompression, noncontiguous fusions, prior lumbar fusions, and other interbody devices were excluded. Primary outcomes included reoperation for nonunion and ASD. Multivariable Cox proportional hazard regression was used to evaluate risks adjusting for patient characteristics. RESULTS: The study consisted of 1377 cases; 307 ALIF alone and 1070 ALIF+PSF. Mean follow-up time was 5.6-years. 5-year crude nonunion incidence was 2.4% for ALIF only and 0.5% for ALIF+PSF; after adjustment for covariates, a lower operative nonunion risk was observed for ALIF+PSF (HR = 0.22, 95% CI = 0.07-0.70). Of patients deemed potentially suitable for ALIF alone, one would need to add PSF in 53-patients to prevent one case of operative nonunion at a 5-year follow-up (number needed to treat). Five-year operative ASD incidence was 4.3% for ALIF only and 6.2% for ALIF+PSF; with adjustments, no difference was observed between the cohorts (HR = 0.96, 95% CI = 0.53-1.74). CONCLUSIONS: While addition of posterior instrumentation in ALIFs is associated with lower risk of operative nonunion compared to ALIF alone, it is rare in both techniques (&lt;5%). Accordingly, surgeons should evaluate added risks associated with addition of PSF, and rather reserve PSF for patients at higher risk for operative nonunion. Rates of operative ASD were not statistically higher with addition of PSF suggesting concern regarding future ASD may be less supported.

Perioperative and safety outcomes following tissue-sparing posterior cervical fusion to revise a pseudarthrosis: A multicenter retrospective review of 150 cases.

Posterior cervical fusion (PCF) with lateral mass screws is a favorable treatment option to revise a symptomatic pseudarthrosis due to reliable rates of arthrodesis; however, this technique introduces elevated risk for wound infection and hospital readmission. A tissue-sparing PCF approach involving facet fixation instrumentation reduces the rates of postoperative complications while stabilizing the symptomatic level to achieve arthrodesis; however, these outcomes have been limited to small study cohorts from individual surgeons commonly with mixed indications for treatment. One hundred and fifty cases were identified from a retrospective chart review performed by seven surgeons across six sites in the United States. All cases involved PCF revision for a pseudarthrosis at one or more levels from C3 to C7 following anterior cervical discectomy and fusion (ACDF). PCF was performed using a tissue-sparing technique with facet instrumentation. Cases involving additional supplemental fixation such as lateral mass screws, rods, wires, or other hardware were excluded. Demographics, operative notes, postoperative complications, hospital readmission, and subsequent surgical interventions were summarized as an entire cohort and according to the following risk factors: age, sex, number of levels revised, body mass index (BMI), and history of nicotine use. The average age of patients at the time of PCF revision was 55 ± 11 years and 63% were female. The average BMI was 29 ± 6 kg/m2 and 19% reported a history of nicotine use. Postoperative follow-up visits were available with a median of 68 days (interquartile range = 41-209 days) from revision PCF. There were 91 1-level, 49 2-level, 8 3-level, and 2 4±-level PCF revision cases. The mean operative duration was 52 ± 3 min with an estimated blood loss of 14 ± 1.5cc. Participants were discharged an average of 1 ± 0.05 days following surgery. Multilevel treatment resulted in longer procedure times (single = 45 min, multi = 59 min, P = 0.01) but did not impact estimated blood loss (P = 0.94). Total nights in the hospital increased by 0.2 nights with multilevel treatment (P = 0.01). Sex, age, nicotine history, and BMI had no effect on recorded perioperative outcomes. There was one instance of rehospitalization due to deep-vein thrombosis, one instance of persistent pseudarthrosis at the revised level treated with ACDF, and four instances of adjacent segment disease. In patients initially treated with multilevel ACDF, revisions occurred most commonly on the caudal level (48% of revised levels), followed by the cranial (43%), and least often in the middle level (9%). This chart review of perioperative and safety outcomes provides evidence in support of tissue-sparing PCF with facet instrumentation as a treatment for symptomatic pseudarthrosis after ACDF. The most common locations requiring revision were the caudal and cranial levels. Operative duration and estimated blood loss were favorable when compared to open alternatives. There were no instances of postoperative wound infection, and the majority of patients were discharged the day following surgery.

Experimental Study on Solidification of Leachate Sludge with High Salt Content by Waste Incineration Bottom Slag

This paper takes the leachate sludge produced from the Guangzhou refuse landfill as the research object and selects sulfoaluminate cement as the fixation to solidify/stabilize the sludge. Meanwhile, bottom-slag is selected as the supplementary fixation. Through unconfined compressive strength test and Scanning electron microscope (SEM), the effect of the mixing amount of cement and bottom-slag on the sludge’s strength is systematically studied. Results show that sulfoaluminate cement can improve the strength of solidified sludge. Sulfoaluminate cement can increase the strength of samples by promoting the hydration reaction, but the effect is better when the content exceeds 40%. When the cement content is fixed, the strength of the sample increases with the bottom slag content. When the bottom slag content exceeds 10%, the proportion of cement in the hydration reaction will decrease, and then the strength of the sample will increase first and then decrease. In addition, under different cement contents, the sample will reach the peak value when the bottom slag content is 10%. Thus, 40% cement + 10% bottom slag is the relative optimal content.

Comparison of Fixation Methods Between Transosseous Pull-Out Suture and Separate Vertical Wiring for Inferior Pole Fracture of Patella: A Systematic Review and Meta-Analysis.

To compare, in a systematic review, Krakow transosseous (KT) suturing and separate vertical wiring (VW) fixation methods in inferior pole fractures of the patella and to evaluate whether the supplementary fixation affected bone union. The MEDLINE, Embase, and Cochrane databases were searched from inception to January 15, 2023. The keywords were "patella inferior pole fracture", "patella distal pole fracture", "transosseous", "pull-out suture", "reattachment", and "vertical wiring". All clinical studies describing KT or VW techniques for inferior pole fracture of the patella and reporting bone union-related complications were included. This meta-analysis included 16 studies with 274 patellae. Demographic data, surgical techniques, clinical outcomes, and complication rates were recorded. The Methodological Index for Non-Randomized Studies criteria were used to assess their quality. A meta-analysis was performed using random-effects models and meta-regression. The meta-analytic estimate of bone union-related complications was 3.8% (95% CI, 1.6%-6.0%) for either PO or VW techniques in inferior pole fractures of the patella. The bone union-related complication rates did not differ significantly between the two techniques (KT, 5.7%; VW, 3.0%; P = .277). Meanwhile, supplementation fixation was significantly associated with decrease in bone union-related complication rates ( p = .013). Fixation of inferior pole fractures of the patella using either KT or VW techniques provided satisfactory and similar clinical results with minimal bone union-related complications. Supplementary fixation has a positive impact on reducing bone union-related complications in inferior pole fractures of the patella following KT and VW techniques. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Computational analysis of the biomechanical stability of internal fixation of the lateral tibial plateau fracture: A mechanical stability study.

The selection of internal fixation as the primary fixation modality for the patient is one of the challenges for the surgeon treating the patient in question. A model of the lateral tibial plateau fracture was established. Three different configurations of internal fixators namely L bone plate, T bone plate, and screw-washer were analyzed. Three stages after surgery were simulated to assess the displacement of bone plates, screws, washers, and the stress shielding ratio in the fracture area.At three stages after surgery, the T bone plate showed better stability for patients during rehabilitation compared with the remaining two schemes, and the screw-washer scheme was the least stable due to the larger internal fixation displacement and stress shielding ratio in the fracture area. In contrast, the L bone plate scheme showed better stability in the early stages after surgery but was second only to the screw-washer scheme in the middle and late stages after surgery. The T bone plate showed better stability and became a new selection for surgeons to treat related patients. At three stages after surgery, the T bone plate has better biomechanical stability compared to the L bone plate and screw-washer schemes.

Implantless Supplementary Fixation of Anterior Cruciate Ligament in Tibia with “Make and Use” Anchor

Supplementary fixation after anterior cruciate ligament reconstruction may be necessary in some situations. There are several methods described for supplementary fixation with their advantages and disadvantages. Anchor fixation is preferred by many because it does not require a second surgery for removal. However, anchors are costly. We described the “make and use” all-suture anchor, which can be made instantly whenever required. We modified “make and use” all-suture anchors for supplementary fixation after ACL reconstruction. This technical note aims to describe the method of supplementary fixation using the “make and use” all-suture anchor.

Human-Robot Joint Misalignment, Physical Interaction, and Gait Kinematic Assessment in Ankle-Foot Orthoses.

Lower limb exoskeletons and orthoses have been increasingly used to assist the user during gait rehabilitation through torque transmission and motor stability. However, the physical human-robot interface (HRi) has not been properly addressed. Current orthoses lead to spurious forces at the HRi that cause adverse effects and high abandonment rates. This study aims to assess and compare, in a holistic approach, human-robot joint misalignment and gait kinematics in three fixation designs of ankle-foot orthoses (AFOs). These are AFOs with a frontal shin guard (F-AFO), lateral shin guard (L-AFO), and the ankle modulus of the H2 exoskeleton (H2-AFO). An experimental protocol was implemented to assess misalignment, fixation displacement, pressure interactions, user-perceived comfort, and gait kinematics during walking with the three AFOs. The F-AFO showed reduced vertical misalignment (peak of 1.37 ± 0.90 cm, p-value < 0.05), interactions (median pressures of 0.39-3.12 kPa), and higher user-perceived comfort (p-value < 0.05) when compared to H2-AFO (peak misalignment of 2.95 ± 0.64 and pressures ranging from 3.19 to 19.78 kPa). F-AFO also improves the L-AFO in pressure (median pressures ranging from 8.64 to 10.83 kPa) and comfort (p-value < 0.05). All AFOs significantly modified hip joint angle regarding control gait (p-value < 0.01), while the H2-AFO also affected knee joint angle (p-value < 0.01) and gait spatiotemporal parameters (p-value < 0.05). Overall, findings indicate that an AFO with a frontal shin guard and a sports shoe is effective at reducing misalignment and pressure at the HRI, increasing comfort with slight changes in gait kinematics.

Finite element analysis comparing a PEEK posterior fixation device versus pedicle screws for lumbar fusion

BackgroundPedicle screw loosening and breakage are common causes of revision surgery after lumbar fusion. Thus, there remains a continued need for supplemental fixation options that offer immediate stability without the associated failure modes. This finite element analysis compared the biomechanical properties of a novel cortico-pedicular posterior fixation (CPPF) device with those of a conventional pedicle screw system (PSS).MethodsThe CPPF device is a polyetheretherketone strap providing circumferential cortical fixation for lumbar fusion procedures via an arcuate tunnel. Using a validated finite element model, we compared the stability and load transfer characteristics of CPPF to intact conditions under a 415 N follower load and PSS conditions under a 222 N preload. Depending on the instrumented levels, two different interbody devices were used: a lateral lumbar interbody device at L4–5 or an anterior lumbar interbody device at L5-S1. Primary outcomes included range of motion of the functional spinal units and anterior load transfer, defined as the total load through the disk and interbody device after functional motion and follower load application.ResultsAcross all combinations of interbody devices and lumbar levels evaluated, CPPF consistently demonstrated significant reductions in flexion (ranging from 90 to 98%), extension (ranging from 88 to 94%), lateral bending (ranging from 75 to 80%), and torsion (ranging from 77 to 86%) compared to the intact spine. Stability provided by the CPPF device was comparable to PSS in all simulations (range of motion within 0.5 degrees for flexion–extension, 0.6 degrees for lateral bending, and 0.5 degrees for torsion). The total anterior load transfer was higher with CPPF versus PSS, with differences across all tested conditions ranging from 128 to 258 N during flexion, 89–323 N during extension, 135–377 N during lateral bending, 95–258 N during torsion, and 82–250 N during standing.ConclusionUnder the modeled conditions, cortico-pedicular fixation for supplementing anterior or lateral interbody devices between L4 and S1 resulted in comparable stability based on range of motion measures and less anterior column stress shielding based on total anterior load transfer measures compared to PSS. Clinical studies are needed to confirm these finite element analysis findings.

Primary anterior lumbar interbody fusion, with and without posterior instrumentation: a 1,377-patient cohort from a multicenter spine registry

BACKGROUND CONTEXTLumbar interbody instrumentation techniques are common and effective surgical options for a variety of lumbar degenerative pathologies. Anterior lumbar interbody fusion (ALIF) has become a versatile and powerful means of decompression, stabilization, and reconstruction. As an anterior only technique, the integrity of the posterior muscle and ligaments remain intact. Adding posterior instrumentation to ALIF is common and may confer benefits in terms of higher fusion rate but could contribute to adjacent segment degeneration due to additional rigidity. Large clinical studies comparing stand-alone ALIF with and without posterior supplementary fixation (ALIF+PSF) are lacking. PURPOSETo compare rates of operative nonunion and adjacent segment disease (ASD) in ALIF with or without posterior instrumentation. STUDY DESIGNRetrospective cohort study. PATIENT SAMPLEAdult patients (≥18 years old) who underwent primary ALIF for lumbar degenerative pathology between levels L4 to S1 over a 12-year period. Exclusion criteria included trauma, cancer, infection, supplemental decompression, noncontiguous fusions, prior lumbar fusions, and other interbody devices. OUTCOME MEASURESReoperation for nonunion and ASD compared between ALIF only and ALIF+PSF. METHODSReoperations were modeled as time-to-events where the follow-up time was defined as the difference between the primary ALIF procedure and the date of the outcome of interest. Crude cumulative reoperation probabilities were reported at 5-years follow-up. Multivariable Cox proportional hazard regression was used to evaluate risk of operative nonunion and for ASD adjusting for patient characteristics. RESULTSThe study consisted of 1,377 cases; 307 ALIF only and 1070 ALIF+PSF. Mean follow-up time was 5.6 years. The 5-year crude nonunion incidence was 2.4% for ALIF only and 0.5% for ALIF+PSF; after adjustment for covariates, a lower operative nonunion risk was observed for ALIF+PSF (HR=0.22, 95% CI=0.06–0.76). Of the patients who are deemed potentially suitable for ALIF alone, one would need to add posterior instrumentation in 53 patients to prevent one case of operative nonunion at a 5-year follow-up (number needed to treat). Five-year operative ASD incidence was 4.3% for ALIF only and 6.2% for ALIF+PSF; with adjustments, no difference was observed between the cohorts (HR=0.96, 95% CI=0.54–1.71). CONCLUSIONSWhile the addition of posterior instrumentation in ALIFs is associated with lower risk of operative nonunion compared with ALIF alone, operative nonunion is rare in both techniques (<5%). Accordingly, surgeons should evaluate the added risks associated with the addition of posterior instrumentation and reserve the supplemental posterior fixation for patients that might be at higher risk for operative nonunion. Rates of operative ASD were not statistically higher with the addition of posterior instrumentation suggesting concern regarding future risk of ASD perhaps should not play a role in considering supplemental posterior instrumentation in ALIF.

Dependence of Total Ankle Tibial Baseplate Stability Upon Bone Density

Category: Ankle Arthritis Introduction/Purpose: The success of total ankle replacement (TAR) in improving patient outcomes is linked to its initial stability after implantation. Limiting early micromotion between implant and bone improves longer-term stability. Tibial component design fixation features play a critical role in determining early stability, with retention of medial and lateral bone sidewalls and interference press-fit both used to supplement fixation. However, tibial component stability is likely also influenced by regional bone density characteristics, and the exact relationship between the two is not adequately understood. The goal of this study was to investigate how bone density affects tibial component stability and bone-implant interface micromotion between the tibial component of a specific TAR and the distal tibia, by using finite element analysis (FEA) during simulated gait. Methods: A commercially available TAR tibial component baseplate was virtually inserted into a computer model of the distal tibia from two patients with end-stage ankle arthritis. These patients were selected based on having different bone density profiles in the affected ankle. The tibia models were generated from patient CT scans, having a CT density-based inhomogeneous material distribution (Fig. 1a) that allowed for bone compaction after press-fit. The tibial component was modeled as titanium alloy material. Two different fixation cases were simulated using FEA: (1) retained medial/lateral sidewalls + line-to-line fit, and (2) retained sidewalls + 50µm interference press-fit. FEA was performed using body weight-scaled kinetic (forces/moments) profiles representing the stance phase of gait, applied to the distal implant surface, while the proximal tibia was held fixed. Press-fit was simulated prior to gait simulation (interference press-fit cases). Micromotions were defined as displacement differences between bone-implant closest nodal pairs, computed from FEA output. Results: For the case with sidewalls+line-to-line fit, micromotions were largest early and late in the stance phase of gait (Fig. 1b), with the largest micromotions observed at heel strike (0% stance). Dorsiflexion and inversion moments dominate in early stance, stressing the anterior edge of the tibia in contact with the implant, leading to relatively large posterior/lateral gapping (Fig. 1b, inset). The observed differences in micromotion between the two patients correlated with differences in bone quality at the tibia contact surface, particularly around the implant pegs (Fig. 1a). However, when interference press-fit was modeled, the differences in micromotion between the two subjects largely disappeared (Fig. 1c), as adequate bone compaction was generated around the interference regions with sufficient bone quality to resist micromotion (Fig. 1d). Conclusion: This study presents novel insight into the effect of TAR fixation features and the associated micromotion at the bone- implant interface in patients with varying distal tibia bone density. We found the stability of the tibial implant to be considerably affected by surrounding bone quality, but the influence of bone quality on implant stability was minimized when interference press- fit was introduced. While a more comprehensive understanding of TAR implant features and their performance is needed, we believe the results of this study clearly demonstrate the importance of bone quality and particularly implant interference press-fit in the stability of TAR implants.

Dependence of Total Ankle Tibial Baseplate Stability Upon Device Fixation Features

Category: Ankle Arthritis Introduction/Purpose: Patient outcomes and construct longevity after total ankle replacement (TAR) are both linked to initial implant stability. Limited early micromotion between the implant and bone encourages stability. Tibial component design fixation features play a critical role in determining the initial stability, with retention of medial and lateral bone sidewalls and interference press-fit used to supplement fixation. The goal of this study was to characterize micromotion between the tibia and baseplate using finite element analysis (FEA) to determine how baseplate design features influence stability. Methods: Three commercially available TAR tibial component baseplate designs were virtually inserted into a computer model of the distal tibia of an end-stage ankle arthritis patient (Fig. 1a). Implant insertion was simulated using FEA for each tibial component with two different fixation cases: (1) no sidewalls+line-to-line fit and (2) sidewalls retained+50µm interference press-fit. Tibia models were derived from patient CT scans, with element-by-element material properties assigned based upon CT Hounsfield units. The tibial components were assigned titanium alloy properties. Following simulated implantation, FEA was performed using kinematic and kinetic profiles representing the stance phase of gait. Loads/moments scaled to patient body weight were applied to the implant (Fig. 1b, 1c), while the proximal tibia was held fixed. Micromotions were defined as the displacement difference between bone-implant closest nodal pairs, computed from FEA output using custom-written code. Results: Amongst tibial component designs inserted without sidewalls and with line-to-line fit, relatively large micromotions were observed. Micromotion differences at heel strike between Peg Designs 1 and 2 may be attributable to sidewall height, while Peg Design 3 was less susceptible to the proximal forces and dorsiflexion moments dominant in early stance (Fig. 1d), potentially because of its angled anterior pegs. Micromotions in Peg Design 3 were largest near toe off, where the plantarflexion moment and decreased proximal force may have permitted motion along the pegs. Differences in micromotion between the different implant designs over the stance phase of gait were greatly reduced when interference press-fit was modeled (Fig. 1e). Conclusion: This study provides new insight on the relative initial stability afforded by different TAR fixation features across designs. In the absence of interference press-fit, all designs showed micromotions large enough to be concerning. However, when interference press-fit was modeled, all designs performed similarly in terms of initial stability during simulated gait. While a better understanding of the relationships between TAR implant features, patient bone density profiles, and initial stability is still needed, our findings suggest that implant interference press-fit plays an important and dominant role in device performance.