Travis G. Maak

The Contemporary Treatment of Odontoid Injuries

Study Design. Review article. Objective. To outline current concepts regarding the assessment and treatment of odontoid fractures. Summary of Background Data. Odontoid fractures account for 9% to 15% of adult, cervical spine fractures. These injuries usually result from hyperflexion or hyperextension of the cervical spine during low-energy impacts in the elderly or high-energy impacts in the young and middle aged. Neurologic injury associated with these fractures is rare. Methods. A review of pertinent literature was conducted. The information gleaned from this review was summarized. Results. Odontoid fractures should be evaluated with appropriate imaging to assess the fracture itself as well as exclude other contiguous or noncontiguous fractures. The Anderson and D’Alonzo classification system is most commonly used. True type I and III odontoid fractures are generally thought to be relatively stable and are often treated nonoperatively with immobilization. Type II fractures at the base of the odontoid are less stable, and there are differing opinions regarding the precise definition and optimal treatment of these injuries. Nonoperative treatment options for odontoid fractures include external immobilization with a collar or halo. Operative treatment options for odontoid fractures include one of several posterior C1-C2 fusion constructs or anterior odontoid fixation if the fracture pattern is amenable. Conclusions. Despite the frequency of odontoid fractures, there is still much debate regarding the optimal treatment of these fractures, especially the type II fractures. This fact may be because of the absence of an ideal solution for this clinical problem. Certainly, prospective controlled clinical studies are needed.

Effect of graft selection on the incidence of postoperative infection in anterior cruciate ligament reconstruction.

Background Knee joint infection is a potentially devastating complication of anterior cruciate ligament (ACL) reconstruction. There is a theoretical increased risk of infection with the use of allograft material. Hypothesis An allograft ACL reconstruction predisposes patients to a higher risk of bacterial infection. Study Design Cohort Study; Level of evidence, 3. Methods All primary ACL reconstructions performed at our institution between January 2002 and December 2006 were reviewed; 3126 total procedures were identified. A retrospective medical record review was performed to determine the incidence of infection, offending organism, time after surgery until presentation, infection treatment, and graft salvage as an outcome of graft choice. Results Of the 3126 ACL reconstructions, 1777 autografts and 1349 allografts were performed. Eighteen infections were identified (0.58%). Infections occurred in 6 of the 1349 allografts (0.44%), 7 of the 1430 bone-patellar tendon-bone (BPTB) autografts (0.49%), and 5 of the 347 hamstring autografts (1.44%). Five grafts were removed because of graft incompetence or loosening: 3 hamstring tendon, 1 BPTB, and 1 allograft. The most common organism isolated was Staphylococcus aureus. Hamstring tendon autograft had an increased incidence of infection compared with both BPTB autograft and allograft (P < .05), with a trend toward a more common need for graft removal (P = .09). Allograft reconstructions were equally likely to have graft salvage as autograft reconstructions. Conclusion Hamstring tendon autografts have a higher incidence of infection than BPTB autografts or allografts. The use of allograft material in ACL reconstructions does not increase the risk of infection or the need for graft removal with infection.

Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: is the tibial tunnel position most important?

Background: Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint. Purpose: To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions—over the top (OTT), anterior footprint (AT), and posterior footprint (PT)—with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition. Results: A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension. Clinical Relevance: The OTT and anterior tibial tunnel positions better control the Lachman and the pivot shift compared with an ACL graft placed in the posterior aspect of the tibial footprint. However, an anterior tibial tunnel position must be balanced against an increased risk and magnitude of graft impingement in extension.

A Comparison of the Effect of Central Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction and Double-Bundle Anterior Cruciate Ligament Reconstruction on Pivot-Shift Kinematics

Background: Biomechanical differences between anatomical double-bundle and central single-bundle anterior cruciate ligament reconstruction using the same graft tissue have not been defined. Purpose: The purpose of this study was to compare these reconstructions in their ability to restore native knee kinematics during a reproducible Lachman and pivot-shift examination. Study Design: Controlled laboratory study. Methods: Using a computer-assisted navigation system, 10 paired knees were subjected to biomechanical testing with a standardized Lachman and mechanized pivot-shift examination. The navigation system recorded the 3D motion path of a tracked point at the center of the tibia, center of the medial tibial plateau, and center of the lateral tibial plateau with each maneuver. The testing protocol consisted of evaluation in the intact state, after complete anterior cruciate ligament transection, after medial and lateral meniscectomy, and after anterior cruciate ligament reconstruction with (1) a single-bundle center-center or (2) anatomical double-bundle technique. Repeated-measures analysis of variance with a post hoc Tukey test was used to compare the measured translations with each test condition. Results: A significant difference in anterior translation was seen with Lachman examination between the anterior cruciate ligament– and medial and lateral meniscus–deficient condition compared with both the double-bundle and single-bundle center-center anterior cruciate ligament reconstruction (P < .001); no significant difference was observed between reconstructions. The double-bundle construct was significantly better in limiting anterior translation of the lateral compartment compared with the single-bundle reconstruction during a pivot-shift maneuver (2.0 ± 5.7 mm vs 7.8 ± 1.8 mm, P < .001) and was not significantly different than the intact anterior cruciate ligament condition (2.7 mm ± 4.7 mm, P > .05). Discussion: Although double-bundle and single-bundle, center-center anterior cruciate ligament reconstructions appear equally effective in controlling anterior translation during a Lachman examination, analysis of pivot-shift kinematics reveals significant differences between these surgical reconstructions. An altered rotational axis resulted in significantly greater translation of the lateral compartment in the single-bundle compared with double-bundle reconstruction. Clinical Relevance: A double-bundle anterior cruciate ligament reconstruction may be a favorable construct for restoration of knee kinematics in the at-risk knee with associated meniscal injuries and/or significant pivot shift on preoperative examination.

Cytokines in rotator cuff degeneration and repair

The pathogenesis of rotator cuff degeneration remains poorly defined, and the incidence of degenerative tears is increasing in the aging population. Rates of recurrent tear and incomplete tendon-to-bone healing after repair remain significant for large and massive tears. Previous studies have documented a disorganized, fibrous junction at the tendon-to-bone interface after rotator cuff healing that does not recapitulate the organization of the native enthesis. Many biologic factors have been implicated in coordinating tendon-to-bone healing and maintenance of the enthesis after rotator cuff repair, including the expression and activation of transforming growth factor-β, basic fibroblast growth factor, platelet-derived growth factor-β, matrix metalloproteinases, and tissue inhibitors of metalloproteinases. Future techniques to treat tendinopathy and enhance tendon-to-bone healing will be driven by our understanding of the biology of this healing process after rotator cuff repair surgery. The use of cytokines to provide important signals for tissue formation and differentiation, the use of gene therapy techniques to provide sustained cytokine delivery, the use of stem cells, and the use of transcription factors to modulate endogenous gene expression represent some of these possibilities.

Effect of Tunnel Position and Graft Size in Single-Bundle Anterior Cruciate Ligament Reconstruction: An Evaluation of Time-Zero Knee Stability

PURPOSE To determine whether (1) increased graft size with anatomic anterior cruciate ligament reconstruction (ACLR) would confer proportionally increased time-zero biomechanical stability and (2) larger grafts would compensate for the inferior time-zero biomechanical kinematics of nonanatomic, single-bundle ACLR. METHODS Ten cadaveric knees were allocated for single-bundle ACLR in an anatomic, center-center or nonanatomic, posterolateral-to-anteromedial footprint position with hamstring autograft. Medial arthrotomy defined the native anterior cruciate ligament (ACL) tibial and femoral footprints. ACLR was performed with a 6-mm semitendinosus graft in 6-mm tunnels and repeated with a 9-mm semitendinosus and gracilis graft in 9-mm tunnels for each knee. Lachman and instrumented pivot-shift examinations assessed knee stability in the ACL-intact, ACL-deficient, and ACLR conditions. Medial and lateral meniscectomies after ACL transection created reproducible pivot shifts. Significance was defined as P < .05. RESULTS ACLR in the center-center or posterolateral-to-anteromedial position significantly reduced anterior tibial translation compared with the ACL- and meniscus-deficient conditions (P < .001). Larger graft size, however, did not significantly improve time-zero biomechanical stability compared with a smaller graft in the same position for either reconstruction (P = .41 to .74). A center-center ACLR controlled tibial translation significantly better than a nonanatomic graft position regardless of graft size (P < .001). A smaller graft in the anatomic position controlled tibial translation significantly better than a larger graft in a nonanatomic position (P < .001). CONCLUSIONS This study showed that increasing graft size did not improve the time-zero biomechanical stability of the knee after ACLR. Increased graft size did not compensate for the biomechanical instability documented with the nonanatomic tunnel position. Restoration of native footprint anatomy in ACLR is of paramount importance regardless of graft size and source. CLINICAL RELEVANCE A larger graft size does not ameliorate the inferior time-zero biomechanics associated with nonanatomic tunnel preparation during single-bundle ACLR.

The Effect of NSAID Prophylaxis and Operative Variables on Heterotopic Ossification After Hip Arthroscopy

Background: Heterotopic ossification (HO) is a known complication of hip arthroscopy. Little is known about the factors that lead to HO after hip arthroscopy. Purpose: The aim of this study was to evaluate the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) and other operative variables on the development of HO. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 357 consecutive cases of hip arthroscopy were retrospectively reviewed over a 3-year period. Routine NSAID prophylaxis was not performed for the first 117 cases. Prophylaxis with naproxen for 3 weeks was then routinely prescribed for the remaining 240 cases. Complete follow-up was available for 288 of the original 357 cases. The presence of HO and its characteristics were recorded for each patient, along with baseline demographic and surgical variables. Odds ratios and logistic regression were used to identify causal factors for HO. Results: The incidence of HO in cases in which the patient did not receive NSAID prophylaxis was 25.0% (23/92) versus 5.6% (11/196) of cases in which the patient received NSAIDs. Patients who received no NSAID prophylaxis were 13.6 times more likely to develop HO postoperatively (95% confidence interval, 2.44-75.5; P = .003). Comparing just mixed-type femoroacetabular impingement resections, patients who received no NSAID prophylaxis were 16.6 times more likely to develop HO postoperatively (95% confidence interval, 2.2-126.0; P = .006). Multivariate logistic regression identified the performance of a mixed-type femoroacetabular impingement resection (P = .011) and the absence of NSAID prophylaxis (P = .003) as predictors of HO development. The majority of HO cases (29/34) occurred in patients with mixed-type femoroacetabular impingement who had both osteochondroplasty and acetabuloplasty. Complications of NSAID therapy in this study population included acute renal failure, hematochezia from acute colitis, and gastritis. Conclusion: Routine NSAID prophylaxis reduces but does not eliminate the incidence of HO in patients undergoing hip arthroscopy. Heterotopic ossification was more likely to develop in patients undergoing acetabuloplasty along with osteochondroplasty and in those who did not receive prophylactic postoperative NSAIDs. Side effects from the investigated NSAID regimen can be serious and should be weighed against the potential benefits in preventing the formation of HO.

Tunnel widening in revision anterior cruciate ligament reconstruction.

&NA; Widening of the tibial and femoral tunnels can present a substantial obstacle during revision anterior cruciate ligament reconstruction because of the associated bone loss and poor graft fixation. Delayed incorporation of soft‐tissue grafts into bone and decreased graft stability are of particular concern. The degree to which mechanical (eg, graft position, fixation method) and biologic (eg, increased cytokine levels, synovial fluid propagation) factors contribute to tunnel widening remains unclear. Radiography, CT, and MRI can be used to characterize the extent of widening and aid in preoperative planning. Although many management methods exist, revision surgery remains difficult. Controversy persists regarding the clinical significance, contributing factors, prophylactic measures, and effective management of tunnel widening following anterior cruciate ligament reconstruction.

Healos/recombinant human growth and differentiation factor-5 induces posterolateral lumbar fusion in a New Zealand white rabbit model.

Study Design. Posterolateral lumbar spine fusions in New Zealand white rabbits. Objective. To evaluate the efficacy of recombinant human growth and differentiation factor-5 (rhGDF-5) lyophilized to a Healos carrier (cross-linked type I collagen with hydroxyapatite coating; DePuy Spine, Inc., Raynham, MA) in inducing fusion. Summary of Background Data. Bone graft substitutes have become an area of considerable interest. rhGDF-5 is one such product. Limited lumbar preclinical studies have been performed with this product. Methods. Single-level, intertransverse process fusions were performed in 67 rabbits using iliac crest autograft (n = 13), Healos alone (n = 13), or 0.5, 1.0, or 1.5 mg/cc rhGDF-5 lyophilized to Healos (n = 13 per group). At 8 weeks, the rabbits were euthanized. Fusion masses were assessed. Results. There were 2 animals (3%) lost to complication. Manual palpation revealed fusion rates for autograft of 38% (5/13), Healos alone of 0% (0/13), and each of the Healos/rhGDF-5 groups of 100% (13/13). Histologic analyses were 95% sensitive and 95% specific for confirming fusion. Histologic differences were found among the treatment groups. Conclusions. In this rabbit fusion model, Healos/rhGDF-5 induced fusion in 100% of the rabbits studied. This rate was significantly higher than the fusion rate induced by autograft (38%). Overall, these results support continued research of Healos/rhGDF-5 as a potential bone graft alternative.

Dynamic Intervertebral Foramen Narrowing During Simulated Rear Impact

Study Design. A biomechanical study of intervertebral foraminal narrowing during simulated automotive rear impacts. Objectives. To quantify foraminal width, height, and area narrowing during simulated rear impact, and evaluate the potential for nerve root and ganglion impingement in individuals with and without foraminal spondylosis. Summary of Background Data. Muscle weakness and paresthesias, documented in whiplash patients, have been associated with neural compression within the cervical intervertebral foramen. To our knowledge, no studies have comprehensively examined dynamic changes in foramen dimensions. Methods. There were 6 whole cervical spine specimens (average age 70.8 years) with muscle force replication and surrogate head that underwent simulated rear impact at 3.5, 5, 6.5, and 8 g, following noninjurious baseline 2 g acceleration. Peak dynamic narrowing of foraminal width, height, and area were determined during each impact and statistically compared to baseline narrowing. Results. Significant increases (P < 0.05) in average peak foraminal width narrowing above baseline were observed at C5–C6 beginning with 3.5 g impact. No significant increases in average peak foraminal height narrowing were observed, while average peak foraminal areas were significantly narrower than baseline at C4–C5 at 3.5, 5, and 6.5 g. Conclusions. Extrapolation of the present results indicated that the highest potential for ganglia compression injury was at the lower cervical spine, C5–C6 and C6–C7. Acute ganglia compression may produce a sensitized neural response to repeat compression, leading to chronic radiculopathy following rear impact.