Patient-reported outcome measures after total knee arthroplasty: a systematic review.

OBJECTIVES: A lack of connection between surgeons and patients in evaluating the outcome of total knee arthroplasty (TKA) has led to the search for the ideal patient-reported outcome measure (PROM) to evaluate these procedures. We hypothesised that the desired psychometric properties of the ideal outcome tool have not been uniformly addressed in studies describing TKA PROMS. METHODS: A systematic review was conducted investigating one or more facets of patient-reported scores for measuring primary TKA outcome. Studies were analysed by study design, subject demographics, surgical technique, and follow-up adequacy, with the 'gold standard' of psychometric properties being systematic development, validity, reliability, and responsiveness. RESULTS: A total of 38 articles reported outcomes from 47 different PROMS to 85 541 subjects at 26.3 months (standard deviation 30.8) post-operatively. Of the 38, eight developed new scores, 20 evaluated existing scores, and ten were cross-cultural adaptation of existing scores. Only six of 38 surveyed studies acknowledged all 'gold standard' psychometric properties. The most commonly studied PROMS were the Oxford Knee Score, New Knee Society Score, Osteoarthritis Outcome Score, and Western Ontario and McMaster Universities Osteoarthritis Index. CONCLUSIONS: A single, validated, reliable, and responsive PROM addressing TKA patients' priorities has not yet been identified. Moreover, a clear definition of a successful procedure remains elusive. Cite this article: Bone Joint Res 2015;4:120-127.

The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity.

BACKGROUND: The prevalence of a cam-type deformity in athletes and its association with vigorous sports activities during and after the growth period is unknown. QUESTIONS/PURPOSES: We therefore compared the prevalence and occurrence of a cam-type deformity by MRI in athletes during childhood and adolescence with an age-matched control group. PATIENTS AND METHODS: We retrospectively reviewed 72 hips in 37 male basketball players with a mean age of 17.6 years (range, 9-25 years) and 76 asymptomatic hips of 38 age-matched volunteers who had not participated in sporting activities at a high level. RESULTS: Eleven (15%) of the 72 hips in the athletes were painful and had positive anterior impingement tests on physical examination. Internal rotation of the hip averaged 30.1° (range, 15°-45°) in the control group compared with only 18.9° (range, 0°-45°) in the athletes. The maximum value of the alpha angle throughout the anterosuperior head segment was larger in the athletes (average, 60.5° ± 9°), compared with the control group (47.4° ± 4°). These differences became more pronounced after closure of the capital growth plate. Overall, the athletes had a 10-fold increased likelihood of having an alpha angle greater than 55° at least at one measurement position. CONCLUSIONS: Our observations suggest a high intensity of sports activity during adolescence is associated with a substantial increase in the risk of cam-type impingement. These patients also may be at increased risk of subsequent development of secondary coxarthrosis. LEVEL OF EVIDENCE: Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Quantification of stem-cement interfacial gaps: in vitro CT analysis of Charnley-Kerboul and Lubinus SPII femoral hip implants.

Interfacial defects between the cement mantle and a hip implant may arise from constrained shrinkage of the cement or from air introduced during insertion of the stem. Shrinkage-induced interfacial porosity consists of small pores randomly located around the stem, whereas introduced interfacial gaps are large, individual and less uniformly distributed areas of stem-cement separation. Using a validated CT-based technique, we investigated the extent, morphology and distribution of interfacial gaps for two types of stem, the Charnley-Kerboul and the Lubinus SPII, and for two techniques of implantation, line-to-line and undersized. The interfacial gaps were variable and involved a mean of 6.43% (sd 8.99) of the surface of the stem. Neither the type of implant nor the technique of implantation had a significant effect on the regions of the gaps, which occurred more often over the flat areas of the implant than along the corners of the stems, and were more common proximally than distally for Charnley-Kerboul stems cemented line-to-line. Interfacial defects could have a major effect on the stability and survival of the implant.

Making minimally invasive THR safe: conclusions from biomechanical simulation and analysis.

The use of smaller surgical incisions has become popularized for total hip arthroplasty (THR) because of the potential benefits of shorter recovery and improved cosmetic appearance. However, an increased incidence of serious complications has been reported. To minimize the risks of minimally invasive approaches to THR, we have developed an experimental approach which enables us to evaluate risk factors in these procedures through cadaveric simulations performed within the laboratory. During cadaveric hip replacement procedures performed via posterior and antero-lateral mini-incisions, pressures developed between the wound edges and the retractors were approximately double those recorded during conventional hip replacement using Charnley retractors (p < 0.01). In MIS procedures performed via the dual-incision approach, lack of direct visualisation of the proximal femur led to misalignment of broaches and implants with increased risk of cortical fracture during canal preparation and implant insertion. Cadaveric simulation of surgical procedures allows surgeons to measure variables affecting the technical success of surgery and to master new procedures without placing patients at risk.

A computerized bioskills system for surgical skills training in total knee replacement.

Although all agree that the results of total knee replacement (TKR) are primarily determined by surgical skill, there are few satisfactory alternatives to the 'apprenticeship' model of surgical training. A system capable of evaluating errors of instrument alignment in TKR has been developed and demonstrated. This system also makes it possible quantitatively to assess the source of errors in final component position and limb alignment. This study demonstrates the use of a computer-based system to analyse the surgical skills in TKR through detailed quantitative analysis of the technical accuracy of each step of the procedure. Twelve surgeons implanted a posterior-stabilized TKR in 12 fresh cadavers using the same set of surgical instruments. During each procedure, the position and orientation of the femur, tibia, each surgical instrument, and the trial components were measured with an infrared coordinate measurement system. Through analysis of these data, the sources and relative magnitudes of errors in position and alignment of each instrument were determined, as well as its contribution to the final limb alignment, component positioning and ligament balance. Perfect balancing of the flexion and extension gaps was uncommon (0/15). Under standardized loading, the opening of the joint laterally exceeded the opening medially by an average of approximately 4 mm in both extension (4.1 +/- 2.1 mm) and flexion (3.8 +/- 3.4 mm). In addition, the overall separation of the femur and the tibia was greater in flexion than extension by an average of 4.6 mm. The most significant errors occurred in locating the anterior/posterior position of the entry point in the distal femur (SD = 8.4 mm) and the correct rotational alignment of the tibial tray (SD = 13.2 degrees). On a case-by-case basis, the relative contributions of errors in individual instrument alignments to the final limb alignment and soft tissue balancing were identified. The results indicate that discrete steps in the surgical procedure make the largest contributions to the ultimate alignment and laxity of the prosthetic knee. Utilization of this method of analysis and feedback in orthopaedic training is expected rapidly to enhance surgical skills without the risks of patient exposure.

Effect of early full weight-bearing after joint injury on inflammation and cartilage degradation.

BACKGROUND: Early full weight-bearing after an acute osteochondral injury avoids problems associated with immobility but may also be harmful by amplifying the inflammatory response. To investigate these effects, we developed an in vivo model of subchondral trauma. METHODS: After an impact injury to the femoral condyle, fourteen dogs were randomized to immediate full weight-bearing or to four weeks of minimal weight-bearing before full weight-bearing. Synovial fluid was sampled by aspiration at one, two, four, eight, twelve, sixteen, twenty, and twenty-four weeks. Neutrophils, monocytes, and lymphocytes were enumerated, and the concentrations of tumor necrosis factor-alpha, interleukin-10, nitric oxide, matrix metalloproteinases, and glycosaminoglycans were measured. RESULTS: Compared with the findings for uninjured joints, the synovial fluid from the impacted joints of full-weight-bearing dogs had significantly higher peak concentrations of neutrophils (p = 0.0006 at one week), mononuclear leukocytes (p = 0.001 at four weeks), tumor necrosis factor-alpha (p = 0.001 at one week), nitric oxide (p = 0.001 at one week), matrix metalloproteinases (p = 0.008 at one week), and glycosaminoglycans (p = 0.002 at four weeks and p = 0.001 at six months). The size of the bone bruise correlated with the peak concentrations of tumor necrosis factor-alpha (r2= 0.89, p = 0.007; Spearman rank test), matrix metalloproteinases (r2= 0.96, p = 0.0004), and glycosaminoglycans (r2= 0.96, p = 0.0004). However, restriction to minimal weight-bearing for four weeks after the injury led to a significant reduction in the synovial fluid concentrations of neutrophils (p = 0.007 at one week and p = 0.01 at two weeks), tumor necrosis factor-alpha (p = 0.0006 to 0.02 during the first four weeks), nitric oxide (p = 0.001 to 0.04 during the first four weeks), and matrix metalloproteinases (p = 0.007 to 0.01 from the second week to the eighth week). In contrast, interleukin-10 concentrations were significantly higher (p = 0.002 at one week) and glycosaminoglycan levels remained at normal levels in animals that were restricted from immediate full weight-bearing after the injury. CONCLUSIONS: The magnitude of the inflammatory response is proportional to the size of the bone bruise. Restriction to minimal weight-bearing for four weeks reduces the magnitude of the inflammatory response and the cartilage degradation following articular cartilage impact injury. CLINICAL RELEVANCE: Strategies to minimize mechanical stress during the early postinjury period may help to preserve cartilage integrity and forestall the development of osteoarthritis.

Cellular events leading to chondrocyte death after cartilage impact injury.

OBJECTIVE: We undertook this study to test our postulate that leukocytes extend the zone of injury in cartilage after acute mechanical trauma. METHODS: Fresh cadaveric canine femoral condyles were subjected to 20-25-MPa impact injury. Condyle explants or dispersed chondrocytes were cultured with autologous blood mononuclear leukocytes (MNLs). Viability of chondrocytes at varying distances from the impact site was assessed by trypan blue exclusion. RESULTS: Mechanical injury caused a significant loss of viable chondrocytes over 7 days, even in cartilage >10 mm from the impact site. After biomechanical stress, death of cells within 10 mm of the impact could be largely prevented by addition of N(G)-monomethyl-L-arginine to inhibit nitric oxide (NO) generation. Chondrocytes within 10 mm of the impact were also susceptible to killing by living MNLs, but not by incubation with the supernatants of endotoxin-activated MNLs. Chondrocytes in this vulnerable zone expressed intercellular adhesion molecule 1 (ICAM-1) (CD54), facilitating attachment of MNLs that localized adjacent to the chondrocytes. Leukocytes killed dispersed chondrocytes harvested from the impact zone by generation of reactive oxygen species. Leukocyte-mediated killing could be blocked by desferoxamine or by antibodies to CD18, which prevent attachment of leukocytes to ICAM-1-expressing chondrocytes. CONCLUSION: Our data suggest that after mechanical injury, chondrocytes distant from the site may be killed through the generation of NO. Inflammatory leukocytes further extend the zone of chondrocyte death by adhering to chondrocytes expressing ICAM-1 and by inducing the accumulation of free oxygen radicals in the chondrocyte cytoplasm. Patients may benefit from therapies that reduce infiltration of inflammatory leukocytes into acutely injured cartilage.

CT analysis of defects of the cement mantle and alignment of the stem: in vitro comparison of Charnley-Kerboul femoral hip implants inserted line-to-line and undersized in paired femora.

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed. When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

Brief report: validation of a system for automated measurement of knee laxity.

OBJECTIVE: To determine the accuracy and repeatability of an automated quantitative fluoroscopic imaging system for measuring knee laxity. DESIGN: Cadaveric validation study. BACKGROUND: Current methods of measuring anterior-posterior laxity lack sufficient accuracy and repeatability. A commercially developed fluoroscopic software package, capable of measuring laxity, required validation. METHODS: Five human cadaveric knees were used. A constant force of 130 N was applied anteriorly and posteriorly in turn to the tibia of each knee with the femur fixed in 30 degrees and 90 degrees of flexion. Quantitative fluoroscopic measurements of anterior-posterior laxity were determined using image analysis software. Fluoroscopic results were compared to the true anterior-posterior displacements of the tibia, which were simultaneously recorded using linear transducers directly attached to the cadaveric specimens. RESULTS: The quantitative fluoroscopic method underestimated laxity by an average of 0.40 mm with a root mean square error of 0.49 mm. The 95% confidence intervals for anterior and posterior laxity error were calculated to be -0.99 to 0.25 mm and -0.89 to 0.03 mm, respectively, where a negative error represents an underestimation. CONCLUSIONS: The quantitative fluoroscopic method offers a dramatic improvement in accuracy over current laxity measurement techniques and acceptable repeatability for assessing ligament damage. RELEVANCE: The considerably more accurate, validated measurement system of this study could improve ligament assessment and diagnosis, and the recognition of injuries otherwise undetected with current methods.

The watershed labral lesion: its relationship to early arthritis of the hip.

This study examined the hypothesis that labral lesions contribute to early degenerative hip disease. Between 1993 and 1999, 436 consecutive hip arthroscopies were performed by the senior author (J.C.M.). In addition, 54 acetabula were harvested from human adult cadavers and 10 hips underwent microangiography to determine labral blood supply. Of the 436 arthroscopic patients, 241 (55.3%) had a total of 261 labral tears, all located at the articular, not capsular, margin of the labrum. Stereomicroscopic examination of the 54 cadaver acetabula revealed a total of 52 labral lesions. Overall, there was no significant difference between the arthroscopic and cadaver populations in terms of the incidence of labral tears (P=.315). There was a high association between labral lesions and adjacent acetabular chondral damage. Arthroscopic and anatomic observations support the concept that labral disruption and degenerative joint disease frequently are part of a continuum of joint pathology.

Experimental and computational simulation of total hip arthroplasty dislocation.

Other than fatal pulmonary embolism and deep infection, dislocation following total hip replacement remains probably the most vexing complication to patient and surgeon. Subluxation and dislocation are complex, poorly understood phenomena. Many important questions in this area unfortunately do not lend themselves well to clinical or registry study. Appropriate realistic laboratory models have been lacking. This article synthesizes new work undertaken independently by two groups of biomechanical investigators using very different, but complimentary, methodologies to study the mechanisms of dislocation, and especially the influence of specific design and surgical variables.

Calcaneocuboid stability: a clinical and anatomic study.

Injuries to the midtarsal joints are relatively uncommon and often unrecognized entities. Acute and chronic instability patterns to the calcaneocuboid joint can occur from such injuries. No previous determinations of normal calcaneocuboid laxity have been reported. Utilizing a previously described technique, stress radiographs were performed in human cadaveric specimens following serial sectioning of the ligamentous supports of the calcaneocuboid joint. Significant differences in calcaneocuboid gap and angle occurred between unstressed and stressed conditions. Cadaveric specimen testing determined that the dorsal and plantar calcaneocuboid ligaments both provide significant contributions to joint stability. Prior to defining pathologic states of joint laxity, normal ranges of stability must be determined. By more clearly defining normal stability of the calcaneocuboid joint and its ligamentous contributions, greater insight into the diagnosis and treatment of calcaneocuboid instability can be obtained.

Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws.

The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction.

Topographic matching of selected donor and recipient sites for osteochondral autografting of the articular surface of the femoral condyles.

The purpose of this study was to define the topography of the articular surface of the femoral condyles and to develop a method for computerized topographic matching of donor and recipient sites for osteochondral transplantation. The condyles of seven fresh cadaveric femurs were mounted on the rotating stage of a laser-based coordinate measuring machine. An anatomic coordinate system defining the articular surface of the condyles was created. Customized software was developed to allow selection and topographic matching of osteochondral graft donor and recipient sites from any location on the surface of the condyles. For cartilage defects within the weightbearing portions of the medial or lateral femoral condyles, grafts taken from sites from the most medial or lateral portions of the patellar groove provided a significantly better topographic match than did grafts taken from the central intercondylar notch.

The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease.

The current authors examined the hypothesis that labral lesions contribute to early degenerative hip disease. Between 1993 and 1999, 436 consecutive hip arthroscopies were done by the senior author. In addition, 54 acetabula were harvested from human adult cadavers. Two hundred forty-one of the 436 (55.3%) patients who had arthroscopies had a 261 labral tears, all located at the articular, not capsular margin of the labrum. Stereomicroscopic examination of the 54 acetabula from cadavers revealed 52 labral lesions. Overall, there was no significant difference between the arthroscopic and cadaveric populations in terms of the incidence of labral tears. (Overall, 73% of patients with fraying or a tear of the labrum had chondral change. Arthroscopic and anatomic observations support the concept that labral disruption and degenerative joint disease are frequently part of a continuum of joint disease.

Long-term residual musculoskeletal deficits after femoral shaft fractures treated with intramedullary nailing.

BACKGROUND: Locked intramedullary (IM) nailing has been recognized as one of the most reliable methods for treatment of femoral shaft fractures. Although IM nails are routinely used in the treatment of these fractures, the long-term effects of retained IM nails are unknown. METHODS: Seventeen patients with radiographically documented healed fracture of femoral diaphysis after locked IM nailing technique were evaluated at a follow-up of at least 18 months postoperatively. All patients had returned to their preinjury level of function and activity before the study. The bone mineral densities (BMD) of the injured and contralateral femora were measured using dual energy x-ray absorptiometry (DEXA). BMD of symmetrical regions in the femoral neck and medial and lateral femoral cortex of the implanted and contralateral femora were compared. Postinjury muscle function was assessed from measurement of the isometric strength of six separate muscle groups (quadriceps, hamstrings, hip extensors, hip flexors, hip abductors, and hip adductors) in treated and control extremities. RESULTS: The average BMD of the femoral neck region of instrumented femora was 9% less than in contralateral control. Within the medial cortex, BMD of the control femora was an average of 20% greater than in the implanted side. In the lateral cortex, the difference averaged 13%. The isometric dynamometric data demonstrated a statistically significant reduction in the strength of the quadriceps of the instrumented extremities as compared with the contralateral ones. There was no significant difference in the strength of the hamstrings, hip extensors, hip flexors, abductors, or adductors. In the control extremities, the average torque generated by isometric contraction of the quadriceps was 3.45+/-1.35 times greater than by the hamstrings. Torque in extension/flexion and abduction/adduction was also observed. CONCLUSION: Our data suggest that limbs with long-term retained IM nails experience a significant reduction in the femur BMD and quadriceps muscle strength. These findings may not be simply related to the implant, and further study is warranted to determine the causes of these changes.

Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length.

Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated.

Quantitative assessment of the midcarpal shift test.

The subjective, clinical midcarpal shift test was compared with a quantitative measurement of carpal volar/dorsal translation versus ulnar deviation using a mechanical testing system. Testing was performed on 19 healthy volunteers (mean age, 33 years) and 3 patients (four wrists; mean age, 23 years) who had been diagnosed with ulnar midcarpal instability, a nondissociative form of carpal instability. During physical examination, each subject's wrist was graded I to V using the previously described classification of the degree of laxity and clunk observed with the midcarpal shift test. Each subject was also evaluated using a quantitative mechanical testing system that simulates the subjective clinical test. The testing system measures displacement of the distal carpal row, more specifically, the capitate, as the wrist is moved from neutral to ulnar deviation under a constant axial load of 44 N directed volarly at the head of the capitate. Reflective markers were attached to the skin above the proximal and distal ends of the third metacarpal and at the point where the 44-N load was applied to the carpus. Motion of the markers was used to calculate ulnar deviation and dorsal/volar translation of the carpus. The maximum slope of the carpal translation versus ulnar deviation curve was measured for each subject and compared with the results of the clinical midcarpal shift test. Higher maximum slopes were seen in subjects with the higher grades of carpal laxity. There were also differences with regard to the point at which the clunk occurred; the higher the clinical grade of laxity, the greater the ulnar deviation of the wrist at the point at which the clunk was observed. These differences were not significant, however. These data confirm the validity of the clinical test and establish its usefulness as a diagnostic indicator of midcarpal nondissociative carpal instability. The mechanized test also may be useful as a biomechanical marker, enabling the results of ligament sectioning to be effectively compared with defined clinical laxity.

Open versus closed repair of the Achilles tendon: an experimental animal study.

This experimental animal study compared the healing patterns between open and closed treatments of Achilles tendon tenotomies. Twenty-four male New Zealand rabbits underwent tenotomy of the left Achilles tendon and were randomized into two groups, treated with either open surgical repair or closed management. After the death of the animal, the retrieved tendons were submitted for biomechanical and histological testing. The total elongation of the open treatment group was 9.5+/-1.0 mm compared with 21.2+/-3.4 mm for the closed treatment group (P = 0.008), and the regain of stiffness was 67.4+/-2.0% and 48.9+/-5.3%, respectively (P = 0.132). Histological evaluation demonstrated similar healing patterns in both groups.

Femoral ring versus fibular strut allografts in anterior lumbar interbody arthrodesis. A biomechanical analysis.

STUDY DESIGN: A comparison between femoral ring and fibular strut allografts in anterior lumbar interbody arthrodesis, as assessed by biomechanical analysis. OBJECTIVES: To assess the difference in stability and rigidity provided by the femoral ring allograft versus that provided by fibular strut allograft. SUMMARY OF BACKGROUND DATA: Two commonly used techniques for spinal arthrodesis at L4-L5 include the femoral ring allograft and the fibular strut allograft. The postoperative stability has not been evaluated biomechanically. METHODS: An anterior lumbar interbody fusion on seven cadaveric specimens was performed using femoral ring and fibular strut allografts. Biplanar radiography was used to measure the 6 degrees of motion of L4 with respect to L5 during a range of loading maneuvers. RESULTS: When an extension moment was applied, the femoral ring allograft extended 4.2 degrees more than the intact specimen, compared with 1.6 degrees with the fibular strut allograft (P = 0.18). When the flexion moment was imposed, lateral bending increased by 2.2 degrees with the femoral ring, compared with 0.7 degree with the fibular strut allograft (P = 0.06). During lateral bending, increased lateral translation was observed to be 0.9 mm with the fibular strut allograft compared with 1.4 mm with the femoral ring allograft (P = 0.06). CONCLUSIONS: Although not statistically significant, the fibular strut allograft creates a more rigid construct immediately after surgery during flexion-extension, lateral bending angulations, and lateral translation. One should consider using the fibular strut allograft over the femoral ring allograft, as it is more stable and rigid construct in the immediate postoperative period.