Femoral Preparation Research Articles

Midterm Results of Fourth-Generation Ceramic-On-Ceramic Total Hip Arthroplasty.

Purpose:There are limited reports for the results of the fourth-generation ceramic-on-ceramic (CoC) articulation total hip arthroplasty (THA). And, throughout the surgical experience, we encountered some cases of liner pulling-out phenomenon after liner fixation and femoral preparation. The objective of this study was to evaluate the incidence, risk factors of delta ceramic liner or head fractures, and also the clinical and radiological results of using the fourth-generation CoC articulation in THA.Patients and Methods:We retrospectively reviewed 242 patients (263 hips) who underwent primary THA using the fourth-generation CoC articulation with a minimum followup of 2 years. Demographic data, Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Patient's satisfactory level were recorded. The radiological evaluation was used to evaluate the implant fixation and complications. Mean followup duration was 5.2 years.Results:Mean HHS and WOMAC score were significantly (P < 0.05) improved at the last followup. About 98.5% of the patients were satisfied with results of the surgery. All acetabular components were placed in adequate position and there was no osteolysis on acetabular or femoral components and subsidence of femoral stem. Four patients showed complications including one-liner fracture.Conclusion:Our midterm study demonstrated excellent clinical and radiological results with only one ceramic liner fracture. Moreover, the results of this study indicate that one possible cause of pulling-out phenomenon is the resonance effect during implantation in Dorr type A patients with the thick cortex. If the surgeon is aware of the liner malposition throughout the operation, the fourth-generation CoC articulation THA could be an outstanding treatment.

Abord antérieur de la hanche en décubitus latéral: description technique avec vidéo opératoire

The direct anterior approach to the hip is judged to be difficult and even after many solutions, such as special operating tables, have been proposed to perform it, in some reports the complication rate remains high. The complications reported are nerve lesions, dislocation, muscles damages, intraoperative fractures. We describe a modification of the anterior approach, undertaken keeping the patient in lateral decubitus, in order to gain a better range of leg movement and a significant reduction of the force applied to the retractors, the technique was named ALDI (anterior lateral decubitus intermuscular) approach. The surgeon starts behind the patient as in all the other traditional approaches, to maintain unchanged the acetabular view and the dexterity in cup implantation. For the femoral preparation, he moves in front of the patient to have a better visualization. In a series of 150 patients, with a mean operative time of 51,38minutes (range, 40–112), we had no intraoperative fractures, one (0,6%) lateral femoral cutaneous nerve temporary neurapraxia, one (0,8%) posttraumatic dislocation four years after the operation and, no revisions for aseptic loosening or infection. At the 5 years follow-up, the mean Oxford Hip score was 45,2 (range, 38–48; SD 2,6), the mean Harris Hip Score was 96,7 (range, 76–100; SD 2,8), and the mean UCLA score was 7 (range, 5–10; SD 1,4). The possibility to always obtain the optimal position of the surgical window with reduced tension on the muscles, and the unchanged initial surgeon position, could make the ALDI approach the ideal technique for the surgeons that decide to perform an anterior approach.

Sex-specific risk factors determine the survivorship of female and male patients after metal-on-metal hip resurfacing.

The need for revision surgery after hip resurfacing arthroplasty (HRA) is more prevalent for women than for men. However, there is a paucity of information to explain this observation. We aimed (1) to determine sex-specific risk factors leading to revision surgery; and (2) to correlate these risk factors to the dominant modes of failure of HRA. 1101 patients (1375 consecutive hips) including 292 women (355 hips) and 809 men (1020 hips) with a mean age of 51.3 years were included regardless of bone quality. The contact patch to rim distance was computed. A contact patch to rim (CPR) distance of ⩽7 mm, an aetiology of developmental dysplasia, a postoperative abduction-adduction arc of ⩾95°, and a metaphyseal stem left uncemented were risk factors associated with revision surgery for female patients, while a CPR distance of ⩽10 mm, a component size of ⩽46 mm, an age at surgery of ⩽55 years, and an early femoral preparation technique were risk factors for male patients. Hips with no risk factors from the female group had a survivorship of 98.7% at 15 years, matching or exceeding the results of all male subgroups. However the risk factors in the female group increased the risk of revision much more than in the male group. In the absence of risk factors, the survivorship of HRA in female patients is equal to that of males. Many female patients can safely benefit from HRA by excluding severe dysplasia and optimising surgical technique.

Hip external rotation and extension angles for exposure and preparation of the proximal femur in direct anterior total hip arthroplasty: A cadaveric study

IntroductionThe direct anterior approach (DAA) to total hip arthroplasty (THA) has a known learning curve, largely due to difficulty achieving exposure and visualization of the acetabulum and proximal femur for joint preparation. There is paucity of information on limb positioning and the degree of angulation at which the limb is positioned for adequate visualization. This study aimed to identify the mean angles of limb positioning necessary for adequate exposure when using two Mueller retractors for femoral preparation using traditional table. Materials & methodsA surgeon performed a DAA THA on 11 cadaveric hemipelves, exposing the femoral canal with two simple, robust Mueller retractors. The degree of external rotation and extension of the hip was measured. ResultsOf the 11, the mean age was 77.6 years and mean BMI was 27.95. The mean external rotation angle was 56.5 ± 13.5°. The mean extension angle was 19.9 ± 6.6°. Discussion & conclusionThe key technical step in this study incorporated a second robust Mueller retractor on the posterior aspect of the greater trochanter, providing maximum leverage to deliver the femur and achieve visibility while reducing angles of limb positioning thereby reducing complications, and ultimately lessening the learning curve.

ALDI (Anterior Lateral Decubitus Intermuscular) approach to the hip: Comprehensive description of the surgical technique with operative video

The direct anterior approach to the hip is judged to be difficult and even after many solutions, such as special operating tables, have been proposed to perform it, in some reports the complication rate remains high. The complications reported are nerve lesions, dislocation, muscles damages, intraoperative fractures. We describe a modification of the anterior approach, undertaken keeping the patient in lateral decubitus, in order to gain a better range of leg movement and a significant reduction of the force applied to the retractors, the technique was named ALDI (anterior lateral decubitus intermuscular) approach. The surgeon starts behind the patient as in all the other traditional approaches, to maintain unchanged the acetabular view and the dexterity in cup implantation. For the femoral preparation, he moves in front of the patient to have a better visualization. In a series of 150 patients, with a mean operative time of 51.38minutes (range, 40–112), we had no intraoperative fractures, one (0.6%) lateral femoral cutaneous nerve temporary neurapraxia, one (0.8%) posttraumatic dislocation four years after the operation and, no revisions for aseptic loosening or infection. At the 5 years follow-up, the mean Oxford Hip score was 45.2 (range, 38–48; SD 2.6), the mean Harris Hip Score was 96,7 (range, 76–100; SD 2.8), and the mean UCLA score was 7 (range, 5–10; SD 1.4). The possibility to always obtain the optimal position of the surgical window with reduced tension on the muscles, and the unchanged initial surgeon position, could make the ALDI approach the ideal technique for the surgeons that decide to perform an anterior approach.

Preparing the femur before the acetabulum does not reduce total blood loss in primary total hip replacement

IntroductionTotal hip replacement is a common and effective surgical intervention for patients with debilitating joint pain but it does represent a significant surgical intervention. For such interventions, blood loss is a potential cause of morbidity and mortality. Optimisation of surgical interventions focuses on reducing such risks. The aim of this study was to determine whether the order of surgical steps, preparing the femur before or after the acetabulum, was associated with the amount of total blood loss in total hip replacement. MethodsWe performed a retrospective study of 100 patients undergoing primary total hip replacement between 2014 and 2018. This was a before and after (interrupted time series) study around the introduction of femur first preparation for total hip replacement in our unit. Fifty patients underwent a standard femoral preparation after placement of the acetabular component. The second 50 patients had the femoral canal prepared and broached prior to the acetabular component. Estimated blood volume and total blood loss associated with the perioperative period were calculated for each patient and a multiple regression analysis performed to account for other patient and surgical variables associated with perioperative blood loss. ResultsThere was a small reduction in total blood loss for the group who underwent femoral preparation prior to acetabular preparation with a mean difference of 39 mls. This difference however was not clinically or statistically (p = 0.392) significant. Gender (p < 0.0001), Body Mass Index (BMI; p < 0.0001), preoperative haematocrit (p < 0.0001), postoperative haematocrit (p < 0.0001) and age (p = 0.004) were the only factors significantly associated with the total volume of blood loss. ConclusionsWhether the femur was prepared before or after the acetabulum did not significantly predict the total volume of blood loss for primary total hip replacement.

Comparison of the Incidence of Intra-operative Fractures in Hip Hemi-arthroplasty Performed in Supine and Lateral Positions.

PurposeThe difficulty of femoral preparation with supine-position hip hemi-arthroplasty (HA) often leads to intra-operative fractures (IOFs). We aimed to clarify the incidence and types of IOFs in HA for hip fractures performed in the supine and lateral positions.Materials and MethodsWe retrospectively investigated cases of HA for acute femoral neck fractures from June 2013 to May 2018. We examined the incidence and types of IOFs according to different approaches. We defined supine-position in HA as the supine and hip-hyperextended (over-range) femoral preparation position, and lateral position as the lateral and hip-flexed femoral preparation position. We used a short tapered wedged stem.ResultsSupine-position HA was used in 46 patients (23.7%) and lateral-position HA in 148 patients (76.3%). IOFs in supine-position HA occurred in 8 patients (17.4%) and included five Vancouver AGT and three Vancouver B2 fractures. IOFs in lateral-position HA occurred in 3 patients (2.0%) and included one Vancouver AGT and two Vancouver B fractures. Supine-position HA was a risk factor for IOFs (adjusted odds ratio, 9.71; 95% confidence interval, 2.37–39.8; P<0.01)ConclusionSupine-position in HA is an IOF risk factor and significantly increases the incidence of great trochanter fractures of Vancouver type A.

Trauma simulation training: a randomized controlled trial ­evaluating the effectiveness of the Imperial Femoral Intramedullary Nailing Cognitive Task Analysis (IFINCTA) tool

Background and purpose — Cognitive task analysis (CTA) has been used extensively to train pilots and in other surgical specialties. However, the use of CTA within orthopedics is in its infancy. We evaluated the effectiveness of a novel CTA tool to improve understanding of the procedural steps in antegrade femoral intramedullary nailing.Material and methods — Design: A modified Delphi technique was used to generate a CTA from 3 expert orthopedic trauma surgeons for antegrade femoral intramedullary nailing. The written and audiovisual information was combined to describe the technical steps, decision points, and errors for each phase of this procedure Validation: A randomized double-blind controlled trial was undertaken with 22 medical students (novices) randomized into 2 equal groups. The intervention group were given the CTA tool and the control group were given a standard operative technique manual. They were assessed using the validated “Touch Surgery™” application assessment tool on femoral intramedullary nailing.Results — The pre-test scores between the two groups were similar. However, the post-test scores were statistically significantly better in the intervention group compared with the control group. The improvement (post-test median scores) in the intervention group compared with the control group was 20% for patient positioning and preparation, 21% for femoral preparation, 10% for proximal locking, and 19% for distal locking respectively (p < 0.001 for all comparisons).Interpretation — This is the first multimedia CTA tool in femoral intramedullary nailing that is easily accessible, user-friendly, and has demonstrated significant benefits in training novices over the traditional use of operative technique manuals.

The minimally invasive AMIS technique for total hip replacement : Video article

Minimally-invasive implantation of atotal hip arthroplasty without damage to or incision of muscles. Osteoarthritis, femoral neck fracture, general indications for total hip arthroplasty. Contraindications for hip arthroplasty. The surgical technique is demonstrated in detail with the help of avideo of the surgical procedure, which is available online: positioning on afracture table with a special leg holder, anterior approach between tensor fasciae latae and rectus femoris muscle, incision of hip capsule and capsular protection, osteotomy of femoral neck in situ, removal of femoral head and acetabular reaming, minimally invasive implantation of acetabular cup, release of pubofemoral ligament and-if necessary-ischiofemoral ligament, external rotation and hyperextension in leg holder with elevation of the proximal femur by ahypomochlion, femoral preparation and implantation of femoral implant, reposition, capsular suture, wound closure. Weight-bearing as tolerated, free movement without limitation of range of motion. Randomized trials and systematic reviews report faster rehabilitation with early mobilization, within the first 3months after surgery; less postoperative pain, less muscle damage and shorter hospital stay; older patients benefit from reduced morbidity and mortality.

Early femoral loosening of the titanium 3M capital cemented hip: A lesson relearned.

A 4-year follow-up study is presented comparing 3M Capital cemented hip replacements with Charnley low friction arthroplasty controls. The mean radiological follow-up in the Capital and Charnley groups was 47 months (25 to 61) and 47 months (23 to 66) respectively. All cases were performed by the same surgical team over the same period (April 1991-October 1993). The operative technique including femoral preparation and cementing technique was identical in each group. Charnley broaches were used for femoral preparation in both groups and Charnley cups were used in all cases. In all of the 3m Capital cases cobalt-chrome femoral heads were used. There was no case selection for either group. Six of the 21 Capital femoral components were deemed to be loose on radiological criteria. None of the Charnley hips was loose. This represents an unacceptably high incidence of radiological femoral stem loosening in the Capital hip replacement. A previous uncontrolled study has attributed early failures to deficient femoral preparation and/or cementing technique. We suggest that early femoral stem loosening in the Capital hip occurs despite satisfactory operative technique in contrast with the results using the Charnley total hip replacement. (Hip International 2002; 1: 17-22).

SuperPath: The Direct Superior Portal-Assisted Total Hip Approach.

The supercapsular percutaneously assisted total hip (SuperPath; MicroPort) approach is a direct superior portal-assisted approach for total hip arthroplasty (THA) that utilizes the interval between the gluteus minimus and the piriformis to access the hip capsule. The technique was developed to promote early mobilization, greater range of motion, and improved pain control. The major steps of this procedure are as follows: Step 1: Patient positioning. The patient is in the standard lateral decubitus position with the involved leg in the "home position," that is, 45° to 60° of flexion, 20° to 30° of internal rotation, and slight adduction by elevating the foot on a padded Mayo stand. Step 2: Surgical exposure. A skin incision is made from the tip of the greater trochanter 6 to 8 cm proximally in line with the femur in the home position, the gluteus maximus muscle is split by blunt dissection in line with the fibers, and the gluteus medius and minimus are retracted anteriorly and the piriformis tendon is retracted posteriorly to access to the capsule without dissecting any muscles. Step 3: Capsular incision. The capsule is incised along the path of the skin incision from the saddle of the femoral neck to 1 cm proximal to the acetabular rim. Step 4: Femoral preparation. A channel is created in the superior aspect of the femoral neck from the femoral canal to the center of the femoral head, using reamers, a round osteotome, and a curet. Step 5: Femoral broaching. Sequential femoral broaches are then used to complete the preparation and size the proximal femoral canal while the head and neck remain intact. Step 6: Neck resection. The femoral neck osteotomy is performed level with the broach neck, and Schanz pins are used to rupture the ligamentum teres and remove the femoral head. Step 7: Acetabular preparation and placement. Acetabular preparation and cup impaction are done through a portal without needing release of the iliotibial band or remaining external rotators. A sharp Romanelli self-retaining retractor (Innomed) and modified Zelpi self-retaining retractor (Life Instruments) are used. Step 8: Trial reduction. Trial reduction is completed using a bone hook and a T-handle to gently manipulate the femur. Step 9: Final implant assembly. Liner impaction is completed through the portal, and the remaining components are implanted. Step 10: Closure. Closure is limited to the capsule, fat, and skin, since no muscles are dissected during this procedure. A recent multicenter study describing nearly 500 SuperPath THAs noted a 30-day all-cause readmission rate of 2.3% and a transfusion rate of 3.3%5. The average length of stay was 1.6 days, with 91% of patients discharged home; 4.1%, to skilled nursing facilities; 3.8%, to home care; and 0.6%, to inpatient physical therapy facilities6.

Primary total hip arthroplasty through a direct anterior approach using a bikini incision: surgical technique

The direct anterior approach (DAA) to the hip has gained popularity with many potential early outcomes benefits for primary total hip arthroplasty (THA). The bikini type oblique incision has been proposed to help with the cosmetic appearance of the scar in conjunction with this approach. In this article, we describe the surgical technique of performing a DAA using a bikini incision. The important keys to the acetabular and femoral preparation and exposure during this technique are retractor placement and use of offset instruments when needed to ensure safe preparation and satisfactory seating of the final implants. The preliminary results of the bikini type incision is promising and offer all of the benefits of the DAA for primary THA, with additional advantage of an improved cosmetic appearance of the surgical scar.

One-stage bilateral implantation of acalcar-guided short-stem intotal hip arthroplasty : Minimally invasive modified anterolateral approach in supine position.

ObjectiveOne-stage bilateral, muscle-preserving, calcar-guided implantation technique through the modified minimally invasive anterolateral approach in supine position.IndicationsBilateral primary/secondary osteoarthritis of the hip; bilateral femoral head necrosis; ASA I–III.ContraindicationsASA IV; severe osteoporosis, other factors jeopardizing stable anchorage of cementless, calcar-guided short-stem; infection.Surgical techniqueSupine position. Skin incision. Opening of fascia; blunt dissection, pushing gluteal muscles dorsally with the index finger. Capsulectomy. Individual osteotomy according to preoperative plan to determine short-stem position. Remove femoral head. Prepare acetabulum. Position cup. Femoral preparation with the curved opening awl. Spare greater trochanter and gluteal muscles. Insert trial rasps in ascending sizes with “round-the-corner” technique. Select offset version, then trial reposition with intraoperative radiograph and implantation of the definitive implant. Wound closure. Consultation with the anesthesiologist to confirm a stable patient. Same procedure on contralateral hip.Postoperative managementMobilization on day 1 with immediate full weight bearing. Remove wound drains and urinary catheter (only female patients) on day 2. Intensive protocol of physiotherapy and rehabilitation. Thrombosis prophylaxis. Rehabilitation from day 7.ResultsAlmost 500 patients have undergone surgery since 2010. First consecutive 54 patients (108 hips) prospectively evaluated. After 2 years, Harris Hip Score was 98.8; satisfaction on visual analogue scale was 9.9. Low peri- and postoperative complication rates; no implant revisions.ConclusionThe muscle-sparing approach and the special “round-the-corner” technique in one-stage bilateral procedure leads to rapid mobilization and rehabilitation with excellent early clinical results and high satisfaction rates.

Lateral unicompartmental knee arthroplasty - a challenge

Joint surface replacement in the lateral compartment by unicondylar knee arthroplasty. Lateral unicompartmental osteoarthritis of the knee joint, avascular necrosis of the lateral femoral condyle. Full thickness cartilage defect in the central part of the medial compartment or in the medial aspect of the patellofemoral joint. Instability/contracture of cruciate and collateral ligaments, valgus deformity >15°, valgus deformity not passively correctable, flexion deformity >15°, an intraoperative flexion <100°, failed upper tibial osteotomy, rheumatoid arthritis. Leg positioning in leg holder. Minimally invasive parapatellar lateral arthrotomy. Exposure of the lateral compartment and removal of osteophytes. Attachment of the tibial saw guide. Horizontal cut 7-8 mm below the original tibial plateau with protection of the lateral collateral ligament. Vertical saw cut via an incision in the central aspect of the patellar ligament with an internal rotation of 20°. Femoral preparation. Insertion of the intramedullary rod, positioning of the femoral drill guide directing to the anterior superior iliac spine and drilling the holes. Insertion of the posterior resection guide. Saw cut with protection of the lateral collateral ligament. Insertion of the 0 mm spigot and first milling. Measurement of the extension gap. Insertion of the corresponding spigot (never use aspigot >5 mm). Milling and insertion of the trial components. Application of the anti-impingement guide and anterior and posterior resection of bone. Final preparation of the tibial plateau. Cementing of the components. Mobilization under full weight-bearing with two crutches. With amean follow-up of 1.7-4years, the dislocation rate is about 0-6.6%. Revision-free survival is 90-98%.

Total knee arthroplasty. Patient-specific instruments and implants

This article describes the concept and surgical technique of patient-specific total knee arthroplasty. Patient-specific implants and instruments are designed and fabricated based on computed tomography (CT) data of the leg. The disposable patient-specific drill guides and cutting-jigs are manufactured taking into consideration the anatomical and biomechanical axes of the knee joint and mediating the efficient pre-navigation of the osseous saw-cuts, without the need for additional navigation or balancing aids. The surgical plan is made on the basis of the CT data. The implantation technique comprises the following steps: distal femoral resection, tibial resection, balancing and femur preparation, tibia preparation, optional patellar resurfacing, trialling of the test components, and implantation of the final components. By using this patient-specific implant system, which includes not only personalized, single-use instruments, but also individualized implants, the surgeon is able to provide endoprosthetic treatment that broadly restores the patient's own knee anatomy and knee kinematics. Preliminary studies have proven the concept and data on this technology are promising so far; however, like a new implant, they are usually limited. In particular, comparative long-term clinical data are still to come.

Risk of Stem Undersizing with Direct Anterior Approach for Total HIP Arthroplasty

The direct anterior approach (DAA) for total hip arthroplasty (THA) is claimed to be as effective but less invasive than the conventional posterior approach (PA). However, the higher risk of femoral fracture and soft tissue damage cannot be underestimated. The present authors believe that the difficult femoral exposure and the surgeon's knowledge of possible complications related to femoral preparation may result in a higher rate of undersized stems when compared to PA, even when a short femoral component is employed to minimise these risks. A retrospective study was performed to compare the effective adherence of surgical sizing to preoperative planning in a series of 112 short stem THAs, of which 59 were implanted through PA and 53 through DAA without intraoperative imaging, by a single surgeon skilled in both techniques. the frequency of stems smaller than expected was 3-times higher with DAA than with PA (54.72% vs 16.95%, p&lt;0.001), while the frequency of stems at least 2 sizes smaller than expected was more than 6-times higher with DAA than with PA (24.53% vs 3.39%, p = 0.001). Conversely, no differences of size discrepancy distribution were found for cups and prosthetic heads. Postoperative x-rays confirmed an inferior mean canal fill in the DAA group, but excluded a different incidence of frontal malalignment between the groups. The technical difficulty of femoral preparation and the surgeon's knowledge of possible related complications might lead to implant undersized stems more frequently through DAA than through PA, especially if intraoperative imaging controls are not used.

Incidence and predisposing factors of periprosthetic proximal femoral fractures: a literature review.

The purpose of this review article was to investigate the incidence and predisposing factors for periprosthetic proximal femoral fractures (PFF) following total hip arthroplasty. We performed a comprehensive search of the medical literature in MEDLINE and EMBASE databases to review articles related to PFF, their incidence and risk factors. The incidence of PPF after primary THA was, in general, lower than after revision THA both for intra- and postoperative PFF. The rate of intraoperative PFF ranged from 0.1% to 27.8% and of postoperative PFF from 0.07% to 18%. Predisposing factors for intraoperative PFF are osteoporosis, rheumatoid arthritis, femoral preparation and surgical technique used to insert the rasp or femoral component, the use of press-fit cementless stems, and revision THA. In case of postoperative PFF, the following seem to be significant risk factors: advanced age, female gender, post-traumatic osteoarthritis, osteoporosis and rheumatoid arthritis, proximal femoral deformities, previous surgery of the affected hip, implant type (especially cementless stems and press-fit implantation), technical errors such as cortical perforation, cortical stress risers, low-energy trauma, osteolysis, loosening and revision THA.

Femoral Vessel Blood Flow Is Preserved Throughout Direct Anterior Total Hip Arthroplasty

Posterolateral and anterolateral approach THA disrupts femoral vessel blood flow, however, this has not been established for the direct anterior (DA) approach. Ten patients undergoing primary DA THA had peak vascular flow rates for the femoral artery and vein calculated via Doppler ultrasound at specified points: incision, acetabular preparation, femoral preparation and final reduction. Peak femoral arterial and venous flow decreased over baseline, but not significantly, during acetabular preparation (P=0.88, P=0.98) and femoral preparation (P=0.97, P=0.97). At final reduction, arterial peak flow was restored (P=1) with an increase in venous flow (P=0.55). Although there were alterations to peak flow, no vessel occlusion occurred at any point during DA THA.

CORR Insights®: A new method for calculating femoral anterior cortex point location and its effect on component sizing and placement.

T he study by Mahfouz and colleagues provides a number of interesting arguments regarding distal femoral preparation in TKA. Traditional instrumentation systems provide surgeons with flexibility in component placement; however, these systems can introduce potential errors in alignment and bone resection planes. Different knee systems have variable implant thicknesses and progression between sizes, making instrumentation comparisons even more difficult. The use of computer navigation or patient-specific guides may eliminate some of these errors but can potentially create new ones. With computer navigation, inaccuracies in registration may create erroneous alignment and resection planes. Any movement of fixed referencing guides can also lead to incorrect resection planes. For patient-specific guides, incorrect templating for surgical planning, or incorrect placement of the cutting guide may lead to incorrect resection planes. Furthermore, to balance the ligaments with patientspecific guides, additional bone resection is often required. In addition, the distal femoral anatomy shows significant variation between individuals and current total knee implants can only approximate that anatomy. While alignment is important, the success of a TKA may be better defined by the kinematics of the reconstructed whole. This paper demonstrates some of the variability that can occur based on the use of specific landmarks for distal femoral bone preparation. The greatest variation detected was in the amount of posterior condylar bone resected with the various techniques. This error is inherent in systems that use anterior cortical referencing and is clearly shown by the data. The use of a PCA+3 posterior condylar resection may be correct in many knees, but when using a ligament balancing technique could be shown to be incorrect as much as 40% of the time. The distal femoral flexion discrepancy between the mechanical axe (MA)-1 and MA-2 technique raises an important point with regard to positioning of the femoral implant. Relative extension of the distal femoral cut will alter This CORR Insights is a commentary on the article ‘‘A New Method for Calculating Femoral Anterior Cortex Point Location and Its Effect on Component Sizing and Placement’’ by Mahfouz and colleagues available at: DOI: 10.1007/s11999-0143930-1. The author certifies that he, or any member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR or the Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999-0143930-1. D. A. Fisher MD (&) Center for Joint Replacement, Indiana Orthopedic Hospital, 8450 Northwest Blvd, Indianapolis, IN 46278, USA e-mail: dafisher@orthoindy.com; dafishermd@aol.com CORR Insights Published online: 7 October 2014 The Association of Bone and Joint Surgeons1 2014

Mid-term outcomes after distally locked-to-standard primary stem exchange in 29 hip-prosthesis patients

BackgroundCementless locked femoral stems are used for revision surgery in patients with bone loss to induce spontaneous bone reconstruction, allowing subsequent replacement by a standard primary stem. The small number of patients and short follow-ups available to date preclude a valid assessment of this strategy. HypothesisAfter distally locked stem revision, replacement by a standard primary stem does not induce complications, and the quality of the bone reconstruction allows strong fixation of a regular primary stem. Materials and methodsWe retrospectively evaluated 29 patients in whom a distally locked femoral stem was replaced by a standard primary stem between 1998 and 2010 (cemented in 27, cementless in 2 cases). The reason for the procedure was stem breakage, stem migration, or thigh pain. Mean patient age was 63years (range, 39–78years). Outcomes were evaluated based on the Postel-Merle d’Aubigné [PMA] score and Harris Hip Score [HHS]. In addition, radiographs were obtained to assess prosthesis fixation and the Hofmann cortical index measured the bone reconstruction. ResultsThe distally locked stem was removed via a postero-lateral approach without femoral osteotomy in all the 29 cases. In one patient, an intra-operative fracture occurred during femoral preparation. Mean follow-up after the exchange procedure was 75months (range, 3–188months). Postoperative ccomplications occurred in 9 (32%) patients and consisted of chronic infection in 2 patients (after 3 and 76months), post-traumatic peri-prosthetic fractures treated with internal fixation in 3 patients (after 100, 138, and 182months), aseptic loosening in 3 patients (after 13, 39, and 122months), and recurrent instability in one patient (after 63months). All cause revision stem survival after 75months was 72% (95% confidence interval, 47%–87%). In the 19 patients who still had their revision stem at last follow-up, the mean PMA score was 16.7 (range, 13–18) and the mean HHS was 88.2 (range, 59–99). The Hofmann index remained unchanged [36.5% (range, 28%–58%) before the exchange and 32.9% (range, 20%–57%) after the exchange; P=0.129]. DiscussionThis study confirms the feasibility of substituting a distally locked stem with a standard primary stem. No specific complications occurred and no technical difficulties arose when extracting the long stems. However, the 32% complication rate and, more specifically, the occurrence of loosening in 10% (3/29) of patients mandates caution in the use of this technique, which should not be proposed routinely, and suggests a need for considering cementless fixation of the standard primary stem. Level of evidenceLevel IV, retrospective study.