Johannes F. Plate

Uncemented Total Hip Arthroplasty In Young Adults With Osteonecrosis Of The Femoral Head: A Comparative Study

BACKGROUND The outcome of uncemented total hip arthroplasty in patients with osteonecrosis of the femoral head in general, and in young adults in particular, remains largely unknown. This study evaluated the clinical and radiographic results of uncemented total hip arthroplasty in young adults with osteonecrosis of the femoral head and compared these results to those seen in young adults with osteoarthritis. METHODS Forty-one consecutive patients with osteonecrosis of the femoral head (fifty-two hips) and forty patients with osteoarthritis (fifty-two hips) were treated with an uncemented total hip arthroplasty at our institution. The mean age for the osteonecrosis group was thirty-eight years, and, for the osteoarthritis group, forty-two years. Clinical and radiographic outcomes at a minimum of two years were assessed. RESULTS At a mean duration of follow-up of three years, the functional improvement was significant in both groups (p < 0.05). The outcome was good to excellent for 94% (forty-nine hips) in the osteonecrosis group and 96% (fifty hips) in the osteoarthritis group. There were two revisions in the osteonecrosis group and one revision in the osteoarthritis group. Survivorship free of revision at the time of the latest follow-up was 96.1% for the osteonecrosis group and 98% for the osteoarthritis group. CONCLUSIONS The short-term results of cementless total hip arthroplasty in patients with osteonecrosis of the femoral head were encouraging and comparable with the results of a matched group of patients with osteoarthritis. We await further follow-up to see if these promising results hold true. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Functional problems and arthrofibrosis following total knee arthroplasty.

Improved surgical techniques and multidisciplinary rehabilitation protocols that involve coordination among surgeons, physical therapists, anesthesiologists, and social services personnel have led to excellent knee function and range of motion in a large percentage of patients following total knee arthroplasty. Nevertheless, there remains a small number of patients with persistent dysfunction that is difficult to treat1-4. Functional problems following total knee arthroplasty may be incapacitating as a result of persistent pain5, instability6, and a limited range of motion7. It has been shown recently that there is a direct correlation between a decreased range of motion following surgery and a lower perceived quality of life as evaluated with use of the Short Form-36 health survey questionnaire8. Continued dysfunction for any reason ultimately leads to decreased patient satisfaction. There is controversy about treatment methods for patients for whom initial rehabilitation efforts are unsuccessful following total knee arthroplasty. The reported efficacy of both noninvasive and invasive treatment modalities has been variable, with the percentage of patients obtaining improvement ranging from 0% to 90%3,9-12. Patients who have continued dysfunction despite initial rehabilitation efforts may require revision surgery. However, patients who have well-aligned, well-fixed prosthetic components will likely not benefit from a complete revision. Treatment of arthrofibrosis, scarring, soft-tissue contractures, and/or other soft-tissue dysfunction should involve less invasive treatment protocols before surgical options are considered. Nonoperative treatment modalities for restoring the range of motion include intensive rehabilitation protocols, static or dynamic splinting, injections, and application of serial casts13. Manipulation with the patient under anesthesia and invasive procedures, including arthroscopic debridement, open debridement with or without polyethylene exchange, and complete component revision, have been utilized when initial nonoperative rehabilitation efforts have failed. As a result of the …

Achieving Accurate Ligament Balancing Using Robotic-Assisted Unicompartmental Knee Arthroplasty

Unicompartmental knee arthroplasty (UKA) allows replacement of a single compartment in patients with limited disease. However, UKA is technically challenging and relies on accurate component positioning and restoration of natural knee kinematics. This study examined the accuracy of dynamic, real-time ligament balancing using a robotic-assisted UKA system. Surgical data obtained from the computer system were prospectively collected from 51 patients (52 knees) undergoing robotic-assisted medial UKA by a single surgeon. Dynamic ligament balancing of the knee was obtained under valgus stress prior to component implantation and then compared to final ligament balance with the components in place. Ligament balancing was accurate up to 0.53 mm compared to the preoperative plan, with 83% of cases within 1 mm at 0°, 30°, 60°, 90°, and 110° of flexion. Ligamentous laxity of 1.31 ± 0.13 mm at 30° of flexion was corrected successfully to 0.78 ± 0.17 mm (P < 0.05). Robotic-assisted UKA allows accurate and precise reproduction of a surgical balance plan using dynamic, real-time soft-tissue balancing to help restore natural knee kinematics, potentially improving implant survival and functional outcomes.

Evaluation of in vivo rotator cuff muscle function after acute and chronic detachment of the supraspinatus tendon: an experimental study in an animal model.

BACKGROUND Surgical repair of large chronic rotator cuff tears can be technically demanding because it requires manipulation of a muscle-tendon unit that is scarred, retracted, and stiffer than normal, all of which contribute to increased tension at the repair site. The purpose of the present study was to characterize the in vivo rotator cuff muscle-tendon unit function after acute and chronic injury at surgically relevant preload tensions. METHODS Sixty-two Sprague-Dawley rats were divided into a healthy, uninjured (control) group (n = 22), an acute injury group (n = 20), and a chronic injury group (n = 20) and underwent in vivo muscle force testing and electromyographic testing of the supraspinatus muscle-tendon unit at various preload tensions. RESULTS Preload tension affected the maximum supraspinatus muscle contractile force in all groups (p < 0.05). At the peak tension required to repair an acute tear, there was a 28% to 30% reduction in maximum tetanic contraction amplitude in all groups (p < 0.05). At the peak tension required to repair a chronic tear, there was a 40% to 53% reduction in maximal tetanic contraction amplitude in all groups (p < 0.05). The uninjured (control) group showed increased muscle endurance (p < 0.05) in comparison with the acute injury and chronic injury groups at all preload tensions. The chronic injury group showed reduced compound motor action potential amplitude (p < 0.05). CONCLUSIONS Both the acute and chronic injury groups demonstrated functional impairment related to increasing preload tensions. Higher repair tensions, associated with the chronic injury setting, resulted in greater functional impairment. The present study also demonstrates an association between increased time from rotator cuff tendon injury and impaired in vivo rotator cuff muscle electromyographic findings.

Advanced Age Diminishes Tendon-to-Bone Healing in a Rat Model of Rotator Cuff Repair

Background: Advanced patient age is associated with recurrent tearing and failure of rotator cuff repairs clinically; however, basic science studies have not evaluated the influence of aging on tendon-to-bone healing after rotator cuff repair in an animal model. Hypothesis/Purpose: This study examined the effect of aging on tendon-to-bone healing in an established rat model of rotator cuff repair using the aged animal colony from the National Institute on Aging of the National Institutes of Health. The authors hypothesized that normal aging decreases biomechanical strength and histologic organization at the tendon-to-bone junction after acute repair. Study Design: Controlled laboratory study. Methods: In 56 F344xBN rats, 28 old and 28 young (24 and 8 months of age, respectively), the supraspinatus tendon was transected and repaired. At 2 or 8 weeks after surgery, shoulder specimens underwent biomechanical testing to compare load-to-failure and load-relaxation response between age groups. Histologic sections of the tendon-to-bone interface were assessed with hematoxylin and eosin staining, and collagen fiber organization was assessed by semiquantitative analysis of picrosirius red birefringence under polarized light. Results: Peak failure load was similar between young and old animals at 2 weeks after repair (31% vs 26% of age-matched uninjured controls, respectively; P > .05) but significantly higher in young animals compared with old animals 8 weeks after repair (86% vs 65% of age-matched uninjured controls, respectively; P < .01). Eight weeks after repair, fibroblasts appeared more organized and uniformly aligned in young animals on hematoxylin and eosin slides compared with old animals. Collagen birefringence analysis of the tendon-to-bone junction demonstrated that young animals had increased collagen fiber organization and similar histologic structure compared with age-matched controls (53.7 ± 2.4 gray scales; P > .05). In contrast, old animals had decreased collagen fiber organization and altered structure compared with age-matched controls (49.8 ± 3.1 gray scales; P < .01). Discussion: In a rat model of aging, old animals demonstrated diminished tendon-to-bone healing after rotator cuff injury and repair. Old animals had significantly decreased failure strength and collagen fiber organization at the tendon-to-bone junction compared with young animals. This study implies that animal age may need to be considered in future studies of rotator cuff repair in animal models. Clinical Relevance: With increasing age and activity level of the population, the incidence of rotator cuff tears is predicted to rise. Despite advances in rotator cuff repair technique, the retear rate remains specifically high in elderly patients. The findings of this research suggest that aging negatively influences tendon-to-bone healing after rotator cuff repair in a validated animal model.

Risk of dislocation using large- vs. small-diameter femoral heads in total hip arthroplasty

BackgroundDislocation remains a difficult problem in total hip arthroplasty. Large-diameter femoral heads may lower the incidence of dislocation by enhancing the jump distance and decreasing impingement, but their performance against small-diameter heads has not been assessed. This study compared the mid-term radiographic and functional outcomes of two matched cohorts of patients undergoing total hip arthroplasty who had a high pre-operative risk for dislocation and who received either small-diameter (26- or 28-millimeters) or large-diameter (≥36-millimeters) femoral heads.MethodsAll patients who received large-diameter heads (≥36-millimeter) between 2002 and 2005, and who had pre-operative risk factors for dislocation, were identified in the institution’s joint registry. Forty-one patients (52 hips) who received large-diameter heads were identified, and these patients were matched to 48 patients (52 hips) in the registry who received small-diameter femoral heads.ResultsAt mean final follow-up of 62 months (range, 49 to 101 months), both groups achieved excellent functional outcomes as measured by Harris Hip scores, with slightly better final scores in the large-diameter group (90 vs. 83 points). No patient showed any radiographic signs of loosening. No patient dislocated in the large-diameter femoral head group; the smaller-diameter group had a greater rate of dislocation (3.8%, 2 out of 52).ConclusionsLarge-diameter femoral head articulations may reduce dislocation rates in patients who have a high pre-operative risk for dislocation while providing the same functional improvements and safety as small-diameter bearings.

The Effect of Botulinum Neurotoxin-A on Blood Flow in Rats: A Potential Mechanism for Treatment of Raynaud Phenomenon

PURPOSE Botulinum neurotoxin-A (BoNTA) is used to treat several disorders, including Raynaud phenomenon. Recent investigations cite toxin-induced increases in blood flow, but no mechanism for BoNTAs actions is proposed. This study hypothesized that local application of BoNTA causes arteriolar vasodilation through sympathetic blockade and results in increased blood flow. METHODS Microvascular effects of BoNTA were assessed using a rat cremaster preparation. Cremaster microvascular diameters were measured in the muscle before and after treatment with the muscle paralytic agent gallamine triethiodide. Preparations were then treated with one of the following: BoNTA (4, 6, or 10 units), BoNTA dilution vehicle, or denatured BoNTA. Arteriolar diameters were measured repeatedly over the observation period. Additional preparations were treated with either tetrodotoxin or prazosin and rauwolscine before BoNTA to confirm that the observed vasodilatory responses were the result of sympathetic neural inhibition. RESULTS The BoNTA application resulted in a significant dose-dependent vasodilation (13% to 15%) of observed cremaster arterioles. Control treatments did not cause vasodilation. Both tetrodotoxin and prazosin/rauwolscine treatments elicited similar vasodilatory effects, with no additional vasodilation elicited by BoNTA. Addition of sodium nitroprusside following BoNTA elicited further vasodilation. In addition, systemic arterial pressure was unaffected by the local administration of BoNTA. CONCLUSIONS Local application of BoNTA results in arteriolar dilation that yields an approximate 69% increase in blood flow, without changing systemic arterial pressure. A BoNTA-mediated vasodilation through sympathetic blockade is a likely mechanism to explain the increase in blood flow reported after treatment with the toxin. CLINICAL RELEVANCE The ability of BoNTA to inhibit sympathetic nervous input reduces vasoconstriction, which is the most likely mechanism for improvement seen in Raynaud phenomenon patients following BoNTA injection.

Rotator cuff injuries in professional and recreational athletes.

Professional and recreational athletes involved in contact sports and sports with repetitive overhead motion are at increased risk for rotator cuff tears. Shoulder anatomy, pathology, and biomechanics place unique stress on the rotator cuff tendons during sports activity. Athletes demand effective treatment to quickly return to elite competition. A PubMed search assessed treatment options providing expedited recovery time and return to competition. Twelve of 231 articles fit the objective criteria; 90.5% of professional contact athletes, 40% of professional overhead athletes, and 83.3% of recreational athletes fully recovered following rotator cuff tear surgical repair. Prompt surgical treatment for full-thickness rotator cuff tears may be appropriate for contact athletes and recreational overhead athletes. Although professional overhead athletes have low recovery rates, surgical repair of full-thickness rotator cuff tears may still be indicated. The authors propose a treatment algorithm based on the limited literature (mainly level 4 and 5 evidence).

Biomechanical Contributions of Posterior Deltoid and Teres Minor in the Context of Axillary Nerve Injury: A Computational Study

PURPOSE To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis. METHODS We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis. RESULTS In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed. CONCLUSIONS Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered. CLINICAL RELEVANCE By quantifying the biomechanical role of muscles during submaximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform preoperative planning and permit more accurate predictions of functional outcomes.

Randomized Comparison of Volar Locking Plates and Intramedullary Nails for Unstable Distal Radius Fractures

PURPOSE To compare minimally invasive intramedullary nails (IMN) and volar locking plates (VLP) for the treatment of unstable distal radius fractures by evaluating postoperative subjective, radiographic, and functional outcomes. The hypothesis was that IMN patients would have less pain and required less pain medication in the early postoperative period and returned to work earlier than VLP patients. METHODS Sixty patients with closed, displaced, unstable, extra-articular, metaphyseal fractures of the distal radius were randomized to receive a VLP or an IMN for internal fixation. Functional outcomes (Quick Disabilities of the Arm, Shoulder, and Hand, Michigan Hand Questionnaire), radiographic measurements (ulnar variance, radial height, inclination, and volar tilt), and range of motion were assessed until final follow-up at 2 years after surgery. Narcotic pain medication use was documented for 5 weeks following surgery. RESULTS There were 2 groups of 30 patients with IMN (mean age, 55 ± 14 y) or VLP (mean age, 55 ± 16 y) with similar demographics and comorbidities. Patients with IMN regained extension earlier but had similar range of motion to patients with VLP at final follow-up. There was similar improvement in Michigan Hand Questionnaire, Quick Disabilities of the Arm, Shoulder, and Hand, and strength between groups. Five weeks after surgery, fewer IMN patients required narcotic pain medication (13%) than VLP patients (33%). Radiographic outcomes were similar at final follow-up. There were 3 failures with IMN versus 1 failure with VLP. All 10 employed patients with IMN returned to previous work compared with 10 of the 12 employed patients with VLP. Time to return to work was similar for both groups. CONCLUSIONS In a cohort of similar patients, IMN and VLP provided comparable improvement in functional and radiographic outcomes. Patients with IMN required less narcotic pain medication after surgery than VLP patients. TYPE OF STUDY/LEVEL OF EVIDENCE Therapeutic II.