KNEE PROBLEMS/KNEE SOLUTIONS
| EVALUATION AND TREATMENT OF OSTEOCHONDRITIS DISSECANS —Robert E. Hunter, MD,
Professor of Clinical Orthopedics, Director, Division of Sports Medicine, University of Arizona College of
Medicine, and Director, Arizona Institute for Sports Medicine, Tucson
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| Definition: focal areas of subchondral bone necrosis with secondary involvement of overlying articular cartilage;
surrounding bone remains viable; focal necrosis distinguishes osteochondritis dissecans (OCD)
from global condyle involvement typical of osteonecrosis
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| Etiology: trauma most widely accepted today; trauma cascade—vascular compromise creates subchondral
bone necrosis, leading to loss of subchondral support, softening, and degeneration of cartilage; results
in partial, then complete, separation of osteochondral fragment, subsequent joint degeneration, and osteoarthritis
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 | Envelope of function: graphed as curve combining load and trauma frequency; problems result when either
factor pushes function beyond envelope; risk especially high among children who engage in sports
year-round (no “off season”) and experience repetitive injuries
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| Location: lateral aspect of medial femoral condyle; examine condyle from anteroposterior (AP) and lateral
perspective; classic lesion occurs in zone B of lateral x-ray (triangle formed by posterior femoral articular
cortex and roof of intercondylar notch); bridges zones 2 and 3 on AP view
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| Classification: current standard based on magnetic resonance imaging (MRI); stable lesions classified as
stages I or II; unstable lesions classified as stages III or IV; high signal change on T2 image, at fragment-
bone interface, extending to subchondral bone, that fills defect, or going beneath defect considered key
to determining instability (high signal indicates fluid layer, suggesting communication with joint and unstable
lesion); predictive value 45%; combination of high signal at T2 and high signal at T1 crossing into
subchondral bone raises predictive value to 85%
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| Treatment: depends on lesion location, size, age of patient, and stability
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| Location: prognosis for spontaneous healing poorer in weight-bearing areas (Cahill zone B, either directly
on medial side or directly on lateral side); lateral lesions usually large, involve weight-bearing
areas, and associated with more bony collapse (which occurs earlier); aggressive early treatment indicated
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| Size: larger lesions have worse prognosis; treat aggressively if diameter >2 cm or area >4 cm2 (spontaneous
healing unlikely)
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| Age: use anticipated physis after healing to classify as adult or juvenile OCD (JOCD); adult has epiphyseal
scar with physis closed or closing; some JOCD heals with conservative treatment, but no adult
OCD heals without intervention
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| Stability: some stable lesions heal with conservative treatment; virtually no unstable lesions do
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| Conservative treatment: indicated for JOCD patients with stable lesions; for children, consists of
crutches if full weight-bearing causes pain; if no pain, modify activities (avoid starting-stopping,
cutting, pivoting, twisting, running, and jumping activities; substitute low-impact activities [walking,
bicycle riding, swimming]); casts and braces impractical
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| Outcomes: 50% failure rate, including high risk for detachment and persistence of symptoms
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| Indications for surgery for JOCD: continued symptoms for 12 wk despite good nonoperative treatment;
any evidence of instability on MRI; x-ray or clinical evidence of detachment; presence of loose fragment
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| Surgical options: transchondral drilling easiest; however, benefits only patients with stable JOCD; use
fixation with or without bone grafting for unstable JOCD and in adults with OCD; speaker uses cannulated
screw or headless (Herbert) screw; bioabsorbable headless screws now available; goals of
fixation—stabilize fragment against displacement and rotation; compress fragment slightly to prevent
fluid extravasation; well-compressed stabilized fragments can subside, allowing buried metal to
become prominent; repeat arthroscopy and remove metal at 12 wk; knee should be nonweight-bearing
until then
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| Bioabsorbable screws: radiolucent material (polylactic acid [PLA]) not necessarily bioabsorbable; can
back out, fracture, become prominent on surrounding subsidence, or damage bone; manage as with
metal screws
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| Irreparable lesions: no evidence that microfracture effective; osteochondral autografts—speaker’s treatment
of choice for lesions with depth <8 mm and area <1.5 cm2 ; autologous chondrocyte transplantation—
good or excellent results seen in 91% of patients in series of 58 patients with JOCD or OCD, with
mean lesion area 5.7 cm2 ; fresh allografts—good to excellent outcomes in >90% of OCD patients in
several studies; best if graft age <21 days (never >28 days); partial condylar replacement—an option for
large lesions, but difficult to do; fit must be perfect
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| MANAGEMENT OF ACUTE PATELLAR INSTABILITY —Dr. Hunter
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| Causes: contributing factors include trochlear dysplasia, quadriceps dysplasia, and >20-mm distance from
tibial tubercle to trochlear groove (TT-TG); patellar malalignment (patella alta); scientific support dwindling
for most conventionally accepted causes
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| Consequences: in study of cadavers with complete patellar dislocation, medial patellofemoral ligament
(MPFL) completely ruptured in 80% (clinical experience suggests ≈90% of patients will have complete
MPFL rupture); inferomedial patella avulsion fragment seen in 80%; medial retinaculum damaged in
60%; patella-sided injuries probably reflect medial patellomeniscal ligament (MPML) avulsion; MPFL
usually ruptures on femoral side; >60% of structures that stabilize patella come through MPFL, making
it main stabilizing factor for medial patella; 10% to 15% go through MPML; third is lateral retinaculum;
MPFL most important stabilizer at 0° to 30° of flexion; failure results in acute patellar dislocation; 60%
of patients also sustain osteochondral damage
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| Evaluation: diagnosis challenging; valgus deformity, external rotation, popping sound, acute pain, and effusion
characterize tears of anterior cruciate or medial collateral ligament, as well as patellar subluxation
and dislocation; effusion and positive-apprehension test key factors in evaluation (apprehension sign “almost
universally present”); x-rays should include patellar views taken at 20° of flexion (Merchant views
taken at 45° usually miss patellar instability); MRI of ligament is study of choice
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| Treatment: consider cause and address resulting pathology; balance more important than compression (do
not overconstrain patellofemoral joint); no place for lateral retinacular release; options include proximal
(non-MPFL) reconstruction (medial plication and vastus medialis oblique [VMO] advance effective
but not recommended for acute MPFL rupture); MPFL reconstruction; evaluate history, physical
examination, x-ray, and presence of patellar displacement on 20° view; presence of any bony findings
(avulsion and osteochondral fracture); if x-rays normal—manage conservatively (lateral buttress brace,
straight-leg raises, quadriceps isometrics, full range of motion); no evidence that arthroscopy improves
outcomes; if x-rays abnormal—obtain MRI to identify site of surgery; if MPFL avulsed off medial facet,
perform primary repair; if MPFL completely ruptured, perform primary reconstruction
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| Plication: not recommended for acute injuries
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| Tibial tubercle transfer (TTT): “address the problem where it lies;” if Q angle >20°, speaker combines
proximal reconstruction and TTT
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| ANTERIOR CRUCIATE LIGAMENT IN THE SKELETALLY IMMATURE KNEE: ARE THERE ALTERNATIVES
TO SURGERY ?—Jack T. Andrish, MD, Basic Science Research Director, Cleveland
Clinic Sports Health, and Head, Section of Orthopaedic Research, Cleveland Clinic, Cleveland, OH
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| Unique issues: involve growth plate, susceptibility to injury, and choice of management; expectations of
patients and parents
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| Natural history: still poorly understood; probably worse in children than adults; high risk for further
symptomatic instability; recurrent instability increases risk for injury to secondary restraints, especially
medial meniscus
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| Treatment considerations: accurate diagnosis; child’s and parents’ expectations; emotional maturity of
child and parent (effective management requires cooperation); growth plate disturbance is concern
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| Tibial spine fracture: lack of activity restriction raises risk for further meniscus injury; plain radiographs
may detect fracture (if not displaced, indicates non-operative approach); MRI can show tibial spine
avulsion; if not displaced, treat by immobilizing in extension (displacement should not exceed 3 mm);
failure of extension may indicate need for arthroscopy; treatment does not guarantee stable knee if
interstitial damage to ligament results in lax incompetent structure
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| Interstitial injury: soft-tissue grafts on growth plate possible without interrupting growth; nonoperative
management includes strict activity modification (no plant-and-cut, stop-and-go, jumping, or sudden
deceleration [eg, soccer, football, basketball, gymnastics]), rehabilitation (includes core strengthening;
long-term commitment difficult to obtain from children), and bracing during all waking hours; without
activity restriction, risk for further meniscal injury increased, but outcomes good with strict bracing
and limitation of activities
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| Conclusion: 3-phase program described by Stanitsky recommended; phase 1—establish diagnosis and
protect patient from further injury; phase 2—rehabilitation for motion, strength, and core stability;
phase 3—maintenance (functional bracing and activity modification)
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Suggested Reading
Amis AA: Current concepts on anatomy and biomechanics of patellar instability. Sports Med Arthrosc 15:48,
2007; Dorizas JA, Stanitski CL: Anterior cruciate ligament injury in the skeletally immature. Orthop Clin
North Am 34:355, 2003; Feller JA et al: Surgical biomechanics of the patellofemoral joint. Arthroscopy
23:542, 2007; Gebarski K, Hernandez RJ: Stage I osteochondritis dissecans versus normal variants of
ossification in the knee in children. Pediatr Radiol 35:880, 2005; Jones DG, Peterson L: Autologous chondrocyte
implantation. J Bone Joint Surg Am 88:2502, 2006; Kouzelis A et al: Herbert screw fixation and reverse
guided drillings, for treatment of types III and IV osteochondritis dissecans. Knee Surg Sports Traumatol
Arthrosc 14:70, 2006; Louisia S et al: Transchondral drilling for osteochondritis dissecans of the medial
condyle of the knee. Knee Surg Sports Traumatol Arthrosc 11:33, 2003; Miura K et al: Results of arthroscopic
fixation of osteochondritis dissecans lesion of the knee with cylindrical autogenous osteochondral plugs.
Am J Sports Med 35:216, 2007; Senavongse W, Amis AA: The effects of articular, retinacular, or muscular
deficiencies on patellofemoral joint stability. J Bone Joint Surg Br 87:577, 2005; Stanitski CL: ACL surgery
in children. Orthopedics 22:180, 1999.
Educational Objectives
| The goal of this program is to improve the management of osteochondritis dissecans (OCD) and anterior
cruciate ligament (ACL) injuries in adults and children. After hearing and assimilating this program, the
clinician will be better able to:
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| 1. Describe the difference between OCD and osteonecrosis.
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| 2. Explain the concept of “envelope of function” and how it applies to OCD.
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| 3. List the factors that increase the risk for patellar instability.
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| 4. Evaluate and treat injuries of the medial patellofemoral ligament.
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| 5. Manage juvenile ACL injuries conservatively, using a 3-phase approach.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and planning
committee members to disclose relevant financial relationships within the past 12 months that might
create any personal conflicts of interest. Any identified conflicts were resolved to ensure that this educational
activity promotes quality in health care and not a proprietary business or commercial interest. For
this program, the following has been disclosed: Dr. Hunter has a relevant financial relationship with Smith
& Nephew. Dr. Andrish and the planning committee reported nothing to disclose.
Acknowledgements
Dr. Hunter spoke at Evaluation and Treatment of the Injured Athlete: Sports Medicine Update 2007, held July 30 to
August 3, 2007, in Boston, MA, and sponsored by Boston University School of Medicine. Dr. Andrish was recorded
at A Knee Innovation Summit, held February 11-14, 2007, in Cleveland, OH, and sponsored by the Cleveland
Clinic Foundation. The Audio-Digest Foundation thanks the speakers and the sponsors for their
cooperation in the production of this program.
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