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The Definite Form of the Coxa Plana

Waldenström·Acta Radiol·1922·48 citations·Pediatrics
DOI·PubMed
SummaryAbstract on PubMed →

Waldenström's 1922 paper describes coxa plana (Legg-Calvé-Perthes disease), the term he coined in 1920 for characteristic flattening of the caput, collum, and acetabulum. He follows children from disease onset through skeletal maturity to define the healed 'definite form.' He classifies the residual deformity into three severity groups.

Study Snapshot

Design
Longitudinal case series
Setting: Hospital of St. Göran, Stockholm
Objective
Whether the healed 'definite form' of coxa plana can be defined by following cases from onset to maturity
Outcome(s)
Radiographic form of the healed hip at skeletal maturity
Subjects
37 patients, 42 hips (22 followed to maturity)
Inclusion
  • Coxa plana essentialis
  • Followed from disease onset
  • Observed to conclusion of growth
Exclusion
  • Coxa plana of inflammatory origin (tuberculous, septic)
Follow-up
Up to 13 years; 10 hips followed past age 20

Key Findings

  • Waldenström followed 37 cases (42 hips), of which 22 hips were tracked from onset to skeletal maturity. This long-term cohort let him define what the healed hip actually looks like, rather than guessing the endpoint from single snapshots.
  • He staged the disease into an evolutionary period (initial then fragmentation), a healing period, a growth period, and a definite stage. The definite form is usually reached after the disease has existed 4-6 years, and these stages remain the conceptual basis for modern Perthes staging.
  • He divided the healed 'definite form' into three severity groups:
    –Group 1 (ordinary): rounded caput, distinct from collum and trochanter — 14 of 22 hips
    –Group 2: enlarged anterosuperior caput overlying the trochanter, no visible upper collum — 6 hips
    –Group 3 (most severe): uneven, excavated joint surface, sharp-edged upper pole — 3 hips
  • The healed deformity is stable and does not change once reached, confirmed by cases followed 10-13 years with no change in form. Milder deformities become definite early; the most severe reach final form only late in the growth period.
  • He established the disease is not inflammatory or infectious, correcting the misleading label 'osteochondritis deformans.' The diagnosis of coxa plana essentialis can be made with certainty only during the evolutionary stage.
  • Treatment (rest, extension, immobilization) did not alter the course. Waldenström noted the disease develops in a 'typical and presumably predestined manner whatever one does.'
  • Function was often preserved despite severe deformity. One patient with bilateral maximal deformity retained only flexion yet could play football, cycle, and dance.
  • The residual deformity predisposes to secondary arthritis, with patients presenting around age 50 with hip pain resembling arthritis deformans, because part of the head never participates in articulation.
Board PearlWaldenström defined coxa plana (Perthes) as a non-inflammatory disease that flattens the entire hip joint, staged from fragmentation through healing to a definite deformity.

Clinical Relevance

This is the paper that gave us the vocabulary and the staging framework for Legg-Calvé-Perthes disease. Waldenström's key conceptual move was recognizing the disease is not an infection or inflammation, discrediting 'osteochondritis deformans' and reframing it as a mechanical softening-and-deformation process.

The staging he laid out (initial, fragmentation, reossification/healing, definite/residual) is the direct ancestor of the Waldenström stages you still use to describe where a child sits in the disease course. Knowing the stage tells you whether the head is still deformable, which drives containment decisions.

The three-group severity classification maps onto the enduring clinical truth: the amount of residual femoral head deformity determines long-term outcome. His observation that an incongruent, extra-articular head fragment predisposes to arthritis around age 50 anticipates the modern principle that head sphericity and containment predict adult degenerative disease.

His note that function was preserved despite radiographic severity is a useful reminder that the film and the patient often diverge.

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The Definite Form of the Coxa Plana

Waldenström·Acta Radiol·1922·48 citations·Pediatrics
DOI·PubMed
SummaryAbstract on PubMed →

Waldenström's 1922 paper describes coxa plana (Legg-Calvé-Perthes disease), the term he coined in 1920 for characteristic flattening of the caput, collum, and acetabulum. He follows children from disease onset through skeletal maturity to define the healed 'definite form.' He classifies the residual deformity into three severity groups.

Study Snapshot

Design
Longitudinal case series
Setting: Hospital of St. Göran, Stockholm
Objective
Whether the healed 'definite form' of coxa plana can be defined by following cases from onset to maturity
Outcome(s)
Radiographic form of the healed hip at skeletal maturity
Subjects
37 patients, 42 hips (22 followed to maturity)
Inclusion
  • Coxa plana essentialis
  • Followed from disease onset
  • Observed to conclusion of growth
Exclusion
  • Coxa plana of inflammatory origin (tuberculous, septic)
Follow-up
Up to 13 years; 10 hips followed past age 20

Key Findings

  • Waldenström followed 37 cases (42 hips), of which 22 hips were tracked from onset to skeletal maturity. This long-term cohort let him define what the healed hip actually looks like, rather than guessing the endpoint from single snapshots.
  • He staged the disease into an evolutionary period (initial then fragmentation), a healing period, a growth period, and a definite stage. The definite form is usually reached after the disease has existed 4-6 years, and these stages remain the conceptual basis for modern Perthes staging.
  • He divided the healed 'definite form' into three severity groups:
    –Group 1 (ordinary): rounded caput, distinct from collum and trochanter — 14 of 22 hips
    –Group 2: enlarged anterosuperior caput overlying the trochanter, no visible upper collum — 6 hips
    –Group 3 (most severe): uneven, excavated joint surface, sharp-edged upper pole — 3 hips
  • The healed deformity is stable and does not change once reached, confirmed by cases followed 10-13 years with no change in form. Milder deformities become definite early; the most severe reach final form only late in the growth period.
  • He established the disease is not inflammatory or infectious, correcting the misleading label 'osteochondritis deformans.' The diagnosis of coxa plana essentialis can be made with certainty only during the evolutionary stage.
  • Treatment (rest, extension, immobilization) did not alter the course. Waldenström noted the disease develops in a 'typical and presumably predestined manner whatever one does.'
  • Function was often preserved despite severe deformity. One patient with bilateral maximal deformity retained only flexion yet could play football, cycle, and dance.
  • The residual deformity predisposes to secondary arthritis, with patients presenting around age 50 with hip pain resembling arthritis deformans, because part of the head never participates in articulation.
Board PearlWaldenström defined coxa plana (Perthes) as a non-inflammatory disease that flattens the entire hip joint, staged from fragmentation through healing to a definite deformity.

Clinical Relevance

This is the paper that gave us the vocabulary and the staging framework for Legg-Calvé-Perthes disease. Waldenström's key conceptual move was recognizing the disease is not an infection or inflammation, discrediting 'osteochondritis deformans' and reframing it as a mechanical softening-and-deformation process.

The staging he laid out (initial, fragmentation, reossification/healing, definite/residual) is the direct ancestor of the Waldenström stages you still use to describe where a child sits in the disease course. Knowing the stage tells you whether the head is still deformable, which drives containment decisions.

The three-group severity classification maps onto the enduring clinical truth: the amount of residual femoral head deformity determines long-term outcome. His observation that an incongruent, extra-articular head fragment predisposes to arthritis around age 50 anticipates the modern principle that head sphericity and containment predict adult degenerative disease.

His note that function was preserved despite radiographic severity is a useful reminder that the film and the patient often diverge.

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