Andrew T. Pennock

Prevalence of Abnormal Hip Findings in Asymptomatic Participants A Prospective, Blinded Study

Background: The prevalence of abnormal magnetic resonance imaging (MRI) findings in an asymptomatic population has yet to be determined. Purpose: The purpose of this study was to assess a cohort of asymptomatic people to determine the prevalence of hip lesions. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Forty-five volunteers with no history of hip pain, symptoms, injury, or surgery were recruited for enrollment in this institutional review board–approved study. The subjects underwent a unilateral MRI scan with a Siemens 3.0-tesla scanner. The extremity side evaluated by MRI was alternated. All MRI scans were reviewed by 3 fellowship-trained musculoskeletal radiologists. The scans were mixed randomly with 19 scans from symptomatic patients to blind the radiologists to the possibility of patient symptoms. An abnormal finding was considered positive when 2 of 3 radiologists agreed on its presence. Results: The average age of volunteers was 37.8 years (range, 15-66 y); 60% were men. Labral tears were identified in 69% of hips, chondral defects in 24%, ligamentum teres tears in 2.2%, labral/paralabral cysts in 13%, acetabular bone edema in 11%, fibrocystic changes of the head/neck junction in 22%, rim fractures in 11%, subchondral cysts in 16%, and osseous bumps in 20%. Participants older than 35 years were 13.7 times (95% CI, 2.4-80 times) more likely to have a chondral defect and 16.7 times (95% CI, 1.8-158 times) more likely to have a subchondral cyst compared with participants 35 or younger. No other joint lesions were associated with age. Male subjects were 8.5 times (95% CI, 1.2-56 times) more likely to have an osseous bump than female subjects. No other joint lesions were associated with sex. Conclusion: Magnetic resonance images of asymptomatic participants revealed abnormalities in 73% of hips, with labral tears being identified in 69% of the joints. A strong correlation was seen between participant age and early markers of cartilage degeneration such as cartilage defects and subchondral cysts.

Analysis of Stored Osteochondral Allografts at the Time of Surgical Implantation

Background To date, the morphological, biochemical, and biomechanical characteristics of articular cartilage in osteochondral allografts that have been stored have not been fully described. Hypothesis Osteochondral allografts procured and stored commercially for a standard period as determined by tissue banking protocol will have compromised chondrocyte viability but preserved extracellular matrix quality. Study Design Controlled laboratory study. Methods Unused cartilage from 16 consecutive osteochondral allografts was sampled during surgery after tissue bank processing and storage. Ten grafts were examined for cell viability and viable cell density using confocal microscopy, proteoglycan synthesis via 35SO4 uptake, and glycosaminoglycan content and compared with fresh cadaveric articular cartilage. Biomechanical assessment was performed on the 6 remaining grafts by measuring the indentation stiffness of the cartilage. Results The mean storage time for the transplanted specimens was 20.3 ± 2.9 days. Chondrocyte viability, viable cell density, and 35SO4 uptake were significantly lower in allografts at implantation when compared to fresh, unstored controls, whereas matrix characteristics, specifically glycosaminoglycan content and biomechanical measures, were unchanged. In addition, chondrocyte viability in the stored allografts was preferentially decreased in the superficial zone of cartilage. Conclusion Human osteochondral allografts stored for a standard period (approximately 3 weeks) before implantation undergo decreases in cell viability, especially in the critically important superficial zone, as well as in cell density and metabolic activity, whereas matrix and biomechanical characteristics appear conserved. The exact clinical significance of these findings, however, is unknown, as there are no prospective studies examining clinical outcomes using grafts stored for extended periods. Clinical Relevance Surgeons who perform this procedure should understand the cartilage characteristics of the graft after 21 days of commercial storage in serum-free media.

Outcomes and Revision Rate After Bone–Patellar Tendon–Bone Allograft Versus Autograft Anterior Cruciate Ligament Reconstruction in Patients Aged 18 Years or Younger With Closed Physes

PURPOSE The purpose of this study was to compare revision rates and outcomes after anterior cruciate ligament (ACL) reconstruction with bone-patellar tendon-bone (BPTB) autografts versus BPTB allografts in patients aged 18 years or younger with closed physes. METHODS Institutional review board approval was obtained for this study. This study included 90 consecutive patients aged 18 years or younger with closed physes who underwent primary ACL reconstruction by a single surgeon between 1998 and 2009, with either BPTB autograft (n = 70) or BPTB allograft (n = 20). Patients who had concomitant ligament injuries were excluded. Outcome measures included the Lysholm score, Tegner activity scale, and patient satisfaction (0, very unsatisfied; 10, very satisfied). Failures were defined as cases requiring ACL revision surgery. RESULTS Of the 90 patients, 79 (88%) were contacted (20 of 20 with allografts and 59 of 70 with autografts). Of these 79 patients, 9 (11%) required revision ACL reconstruction. In the autograft group, 3% (2 of 59) required revision ACL reconstruction at a mean of 15.4 months (range, 13.0 to 17.7 months) after the index procedure. In the allograft group, 35% (7 of 20) required revision ACL reconstruction at a mean of 9.1 months (range, 5.3 to 12.0 months) after the index procedure. The allograft group was 15 (95% confidence interval [CI], 2 to 123) times more likely to require revision reconstruction than the autograft group (P = .001). The mean Lysholm score at follow-up was 85 (95% CI, 80.4 to 90.3) for the autograft group and 91 (95% CI, 88.1 to 97.3) for the allograft group (P = .46). The median Tegner activity scale was 7.0 (95% CI, 6.9 to 8.0) for autograft group and 6.5 (95% CI, 4.9 to 8.4) for the allograft group (P = .27). Median patient satisfaction score was 10 of 10 in both cohorts. No failures were seen in either group at 2 years postoperatively. Five of seven allograft failures occurred because of a premature return to sports. CONCLUSIONS No significant differences in function, activity, or satisfaction were found between allograft and autograft reconstructions in this patient population. The allograft group had a failure rate 15 times greater than that in the autograft group, with all failures occurring within the first year after reconstruction. LEVEL OF EVIDENCE Level III, retrospective comparative study.

Variation in Tibial Tubercle–Trochlear Groove Measurement as a Function of Age, Sex, Size, and Patellar Instability

Background: The tibial tubercle–trochlear groove (TT-TG) measurement was developed to quantify morphologic abnormalities about the knee associated with patellar instability and to help guide surgical decision making. Purpose: To assess variations in TT-TG as a function of patient age and size in a population of patients with patellar instability compared with those with no instability. Study Design: Cross-sectional study; Level of evidence, 3. Methods: All patients younger than 20 years who underwent surgery for patellar instability from 2010 to 2012 were included in this retrospective study. A total of 180 patients with no history of patellar instability or patellofemoral complaints were used as a control group. The TT-TG was measured on magnetic resonance axial images using the centers of the tibial tubercle and the trochlear groove. Data were normalized based on patient height, weight, body mass index (BMI), and femur width. Alpha was set at P < .05 to declare significance. Results: The average age of the 45 patellar instability patients was 15.4 years (range, 10-18 years), their mean TT-TG was 16.3 mm (range, 6.5-26 mm), and 51% were male. By comparison, the mean age of the control group was 16 years (range, 10-19 years), the mean TT-TG was 11.7 mm (range, 3-22 mm), and 58% were male. The TT-TG and the normalized TT-TG for height, weight, BMI, and femur width were all greater in the patellar instability group compared with the control group (P ≤ .001). Thirty-one percent of patients had a TT-TG greater than 20 mm in the instability group compared with 3% in the control group (P < .05, specificity 97%, sensitivity 31%). The TT-TG was found to increase as a function of height in both groups (r = 0.14, P = .04) and decreased with age only in the instability group (r = −0.3, P = .04). Conclusion: An elevated TT-TG is associated with patellar instability both in pediatric and adolescent patients. However, this measurement varies as a function of patient age and height, with each centimeter in height increasing the TT-TG by 0.12. Normalization of TT-TG to patient height may control for size variations and should be undertaken in the work-up and management of patients with patellar instability.

Osteochondral Allograft Transplantation of the Knee in the Pediatric and Adolescent Population

Background: Multiple studies in adults have shown that osteochondral allograft transplantation is an effective treatment option for large chondral and osteochondral defects of the knee. Limited outcome data are available on osteochondral allografts in the pediatric and adolescent patient populations. Purpose: To describe a 28-year experience with osteochondral allograft transplantation in patients younger than 18 years with a focus on subjective outcome measures, return to activities, and allograft survivorship. Study Design: Case series; Level of evidence, 4. Methods: A total of 39 patients (43 knees) underwent fresh osteochondral allograft transplantation for treatment of chondral and osteochondral lesions. Twenty-six male and 17 female knees with a mean age of 16.4 years (range, 11.0-17.9 years) at index surgery were followed-up at a mean of 8.4 years (range, 1.7-27.1 years). Thirty-four knees (79%) had at least 1 previous surgery. The most common underlying causes of the lesions were osteochondritis dissecans (61%), avascular necrosis (16%), and traumatic chondral injury (14%). Mean allograft size was 8.4 cm2. The most common allograft location was the medial femoral condyle (41.9%), followed by the lateral femoral condyle (35%). Each patient was evaluated with the International Knee Documentation Committee pain, function, and total scores; a modified Merle d’Aubigné-Postel (18-point) scale; and Knee Society function score. Failure was defined as revision osteochondral allograft or conversion to arthroplasty. Results: Five knees experienced clinical failure at a median of 2.7 years (range, 1.0-14.7 years). Four failures were salvaged successfully with another osteochondral allograft transplant. One patient underwent prosthetic arthroplasty 8.6 years after revision allograft. Graft survivorship was 90% at 10 years. Of the knees whose grafts were in situ at latest follow-up, 88% were rated good/excellent (18-point scale). The mean International Knee Documentation Committee scores improved from 42 preoperatively to 75 postoperatively, and the Knee Society function score improved from 69 to 89 (both P < .05). Eighty-nine percent of patients reported “extremely satisfied” or “satisfied.” Conclusion: With 88% good/excellent results and 80% salvage rate of clinical failures with an additional allograft, osteochondral allograft transplantation is a useful treatment option in pediatric and adolescent patients.

Development and prevalence of femoroacetabular impingement-associated morphology in a paediatric and adolescent population: A CT study of 225 patients

We investigated the development of CT-based bony radiological parameters associated with femoroacetabular impingement (FAI) in a paediatric and adolescent population with no known orthopaedic hip complaints. We retrospectively reformatted and reoriented 225 abdominal CTs into standardised CT pelvic images with neutral pelvic tilt and inclination (244 female and 206 male hips) in patients ranging from two to 19 years of age (mean 10.4 years). The Tönnis angle, acetabular depth ratio, lateral centre-edge angle, acetabular version and α-angle were assessed. Acetabular measurements demonstrated increased acetabular coverage with age and/or progressive ossification of the acetabulum. The α-angle decreased with age and/or progressive cortical bone development and resultant narrowing of the femoral neck. Cam and pincer morphology occurred as early as ten and 12 years of age, respectively, and their prevalence in the adolescent patient population is similar to that reported in the adult literature. Future aetiological studies of FAI will need to focus on the early adolescent population.

Spectrum of Radiographic Femoroacetabular Impingement Morphology in Adolescents and Young Adults: An EOS-Based Double-Cohort Study

BACKGROUND Symptomatic femoroacetabular impingement is a known prearthritic condition. Impingement morphology is poorly defined in the adolescent population. The purpose of this study was to document the prevalence of radiographic impingement morphology in adolescents with no symptomatic hip problems. METHODS Ninety anteroposterior images of the hip in forty-five consecutive adolescents with scoliosis met the inclusion criteria. Sex distribution was equal. The second cohort (ninety hips) was an age-matched group with no scoliosis. None had symptomatic hip problems. Images were analyzed for coxa profunda, protrusio acetabuli, Tönnis angle, anteroposterior alpha angle, center-edge angle, acetabular crossover, ischial spine sign, and neck-shaft angle. RESULTS Of the 180 hips, 92.8% demonstrated at least one parameter suggesting impingement morphology, whereas 52.2% showed at least two signs. Evidence of coxa profunda was seen in 81.7% of the hips, while a negative Tönnis angle was seen in 31.1% and a center-edge angle indicative of acetabular overcoverage was seen in 15%. An acetabular crossover sign was detected in 27.2% of the hips, while an abnormal anteroposterior alpha angle was found in 5.6% of the hips in male patients and 6.7% of the hips in female patients. Statistical analysis revealed that abnormal alpha angles (p = 0.029), crossover signs (p = 0.029), and ischial spine signs (p = 0.026) were more common in the cohort without scoliosis, and coxa profunda was more common in females (p = 0.034). CONCLUSIONS There was a high prevalence of radiographic impingement morphology beyond the spectrum of normal in this double-cohort study of adolescents. Femoroacetabular impingement remains a dynamic problem, and we caution against relying only on the use of hard-set static radiographic parameters when evaluating femoroacetabular impingement. This study raises the important question of what morphologic characteristics should be defined as abnormal, when at least one finding of impingement morphology is noted in such a large segment of the population. On the basis of the normative data obtained, reference values for radiographic parameters of femoroacetabular impingement morphology should be redefined. Normal values for a Tönnis angle were between -8° and 14°, the upper limit of the center-edge angle was 44°, and the normal values for femoral neck-shaft angle were between 121° and 144°. Surgical indications should be tailored to physical examination findings and not radiographic findings alone.

The Influence of Arm and Shoulder Position on the Bear-Hug, Belly-Press, and Lift-Off Tests An Electromyographic Study

Background: Clinical testing for the integrity of the subscapularis muscle includes the belly-press, lift-off, and bear-hug examinations. While these tests have been widely applied in clinical practice, there is considerable variation in arm positioning within each clinical examination. Hypothesis: To determine the ideal arm and shoulder positions for isolating the subscapularis muscle while performing the bear-hug, belly-press, and lift-off tests. Study Design: Controlled laboratory study. Methods: The activity of 7 muscles was monitored in 20 healthy participants: upper and lower divisions of the subscapularis, supraspinatus, infraspinatus, latissimus dorsi, teres major, triceps, pectoralis major. Electromyogram data were collected and compared across each clinical test at varying arm positions: bear-hug (ideal position, 10° superior, 10° inferior to the shoulder line), belly-press (ideal position, maximum shoulder external rotation, and maximal shoulder internal rotation), and lift-off (ideal position, hand position 5 in. [12.7 cm] superior and 5 in. [12.7 cm] inferior to the midlumbar spine). Results: Regardless of arm and shoulder position, the upper and lower subscapularis muscle activities were significantly greater than all other muscles while performing each test. No significant differences were observed between the upper and lower subscapularis divisions at any position within and across the 3 tests. There were no significant differences in subscapularis electromyogram activities across the 3 tests. Conclusion: The level of subscapularis muscle activation was similar among the bear-hug, belly-press, and lift-off tests. The 3 tests activated the subscapularis significantly more than all other muscles tested but were not different from one another when compared across tests and positions. Although the bear-hug and lift-off tests have been described to activate differential portions of the subscapularis, the findings of this study do not support the preferential testing of a specific subscapular division across the 3 tests. As such, all 3 tests are effective in testing the integrity of the entire subscapularis muscle, although there does not appear to be an ideal position for selectively testing its divisions. Clinical Relevance: Clinicians may feel comfortable in using any of the 3 tests, depending on the patient, to isolate the function of the subscapularis as a single muscle. Furthermore, clinicians should not solely focus on a patient’s arm position when administering an examination but also compare the affected arm to the contralateral shoulder when appropriate.

Pelvic Apophyseal Avulsion Fractures: A Retrospective Review of 228 Cases.

Background: The aim of this study was to assess the patient demographics, epidemiology, mechanism of injury, and natural history of pelvic apophyseal avulsion fractures. Methods: A retrospective records review of imaging and clinical documentation was performed for patients diagnosed with pelvic apophyseal avulsion fractures at our institution from 2007 to 2013. Patient’s Risser score, triradiate status, fracture location, size, and displacement were recorded based on initial injury radiographs. Further clinical and radiographic chart review was utilized to determine mechanism of injury, presence of multiple/bilateral injuries, nonunion, chronic pain, as well as any surgical interventions performed. Results: We identified 225 patients diagnosed with 228 apophyseal avulsion fractures with mean age of 14.4 years. Males represented 76% of the patients. Anterior inferior iliac spine (AIIS) avulsions were the most common, representing 49% of all avulsion fractures, followed by anterior superior iliac spine (30%), ischial tuberosity (11%), and iliac crest (10%). The most common mechanism of injury was sprinting/running (39%) followed by kicking (29%), but the mechanism varied by fracture type with 50% of AIIS avulsions caused by kicking. Multiple pelvic fractures were identified in 6% of patients. Pain >3 months out from initial injury was present in 14% of all patients and AIIS avulsion fractures were 4.47 times more likely to have chronic pain. Five nonunions were identified, 4 of which were ischial tuberosity avulsions. Initial fracture displacement >20 mm increased the risk of nonunion by 26 times. Surgical treatment was indicated in 3% of cases. Conclusions: In this series, nearly all pelvic avulsion fractures (97%) were managed successfully with a conservative approach. Contrary to prior studies, AIIS avulsions represented half of the avulsion fractures. AIIS and ischial tuberosity fractures are at increased risk of developing future pain and nonunions, respectively. Patients and families need to be counseled about this possibility because future intervention may be necessary. Level of Evidence: Level IV—therapeutic.

Does subchondral bone affect the fate of osteochondral allografts during storage

Background Osteochondral allografts currently are hypothermically stored for a minimum of 14 days to a maximum of 28 days before surgical implantation, making storage conditions increasingly important. Previous studies have suggested that graft deterioration during storage may result from degradative factors and residual marrow elements in the subchondral bone. Hypothesis Allografts stored with large bone-to-cartilage ratios will be compromised after prolonged storage compared with grafts with minimal bone. Study Design Controlled laboratory study. Methods Osteochondral plugs were harvested from 16 fresh human femoral condyles and randomly assigned to 1 of 3 groups based on bone-to-cartilage ratios: 1:1, 5:1, or 10:1. These ratios were considered on the basis that the 1:1 ratio is the minimum bone necessary to press-fit an allograft and 10:1 is the present ratio used by tissue banks for allograft storage. After 14 and 28 days of storage at 4 ° C, the specimens were assessed for viability and viable cell density using confocal microscopy, proteoglycan synthesis by 35SO4 incorporation, and glycosaminoglycan content. Results All grafts underwent a significant decline in viable cell density, proteoglycan synthesis, and chondrocyte viability (particularly in the superficial region) after 14 days of storage, but no differences were observed between the 1:1, 5:1, or 10:1 ratio groups at either day 14 or day 28. In addition, no significant difference was noted in the glycosaminoglycan content in any of the groups. Conclusion Osteochondral allografts stored with a 10:1 bone-to-cartilage ratio, similar to tissue-banking ratios, performed no worse than allografts stored with minimal bone, suggesting that the bone-to-cartilage ratio plays little to no role in the degradation of allografts during prolonged storage. Clinical Relevance As the practice of osteochondral allograft resurfacing becomes more commonplace, it is important that surgeons understand the factors that affect graft quality.